Development of a reliable Hg-195m--Au-195m generator for the production of Au-195m, a short-lived nuclide for vascular imaging.

A new mercury-195m (T1/2: 41 hr) leads to gold-195m (T1/2: 30.6 sec) generator suitable for first-pass as well as steady-state radionuclide angiography studies has been developed. The distribution coefficients, Kd, for mercury (Hg-195m) and gold (Au-196), experimentally evaluated on chelating resin Chelex 100, showed this resin to be suitable as the column packing. Mercury-195m in a Trisma buffer solution at pH 7.40 was loaded on a chelating resin Chelex 100 column, together with gold carrier. Au-195m was eluted with an aqueous solution of 5% glucose in a 0.01M Trisma buffer at pH 7.70 (25 degrees C). Chemical assessment of the eluate has ensured that the eluted carrier-free gold is by no means colloidal: 80% is found in an ionic form, 20% as an uncharged species. Safe clinical use for routine diagnosis in humans is possible.

In vivo measurement of carbon-11 thymidine uptake in non-Hodgkin's lymphoma using positron emission tomography.

Carbon-11 thymidine (TdR) uptake using positron emission tomography (PET) has been measured in ten patients with non-Hodgkin's lymphoma (NHL). The rate of TdR uptake (mean +/- s.d.) was of 0.009 +/- 0.006 mumol.100 cc-1.min-1 in low-grade NHL. This rate was 0.063 +/- 0.049 mumol.100 cc-1.min-1 in intermediate-grade NHL and 0.159 mumol.100 cc-1.min-1 in a patient with high-grade NHL. Lymphoma radioactivity reached a plateau at 0.42 +/- 0.22%. 100 cc-1 of the injected dose from 10 min after injection. The highest 11C uptakes were observed in the kidneys and in the liver (3.30 +/- 1.30 and 2.10 +/- 0.05%. 100 cc-1 of the injected dose, respectively). The lymphoma-to-muscle ratio was of 11.8 +/- 1.7, whereas the lymphoma-to-intestine ratio was of 1.5 +/- 0.7. Accordingly, the measurement of [11C]TdR uptake in the abdomen may need other imaging methods for adequate interpretation. The results suggest that [11C]TdR uptake using PET might be a method for noninvasively measuring cell proliferation in vivo.

Accumulation of polymorphonuclear leukocytes in reperfused ischemic canine myocardium: relation with tissue viability assessed by fluorine-18-2-deoxyglucose uptake.

Polymorphonuclear leukocytes may participate in reperfusion injury. Whether leukocytes affect viable or only irreversibly injured tissue is not known. Therefore, we assessed the accumulation of 111In-labeled leukocytes in tissue samples characterized as either ischemic but viable or necrotic by metabolic, histochemical, and ultrastructural criteria. Six open-chest dogs received left anterior descending coronary occlusion for 2 hr followed by 4 hr reperfusion. Myocardial blood flow was determined by microspheres and autologous 111In-labeled leukocytes were injected intravenously. Fluorine-18-2-deoxyglucose, a tracer of exogenous glucose utilization, was injected 3 hr after reperfusion. The dogs were killed 4 hr after reperfusion. The risk and the necrotic regions were assessed following in vivo dye injection and postmortem tetrazolium staining. Myocardial samples were obtained in the ischemic but viable, necrotic and normal zones, and counted for 111In and 18F activity. Compared to normal, leukocytes were entrapped in necrotic regions (111In activity: 207 +/- 73%) where glucose uptake was decreased (26 +/- 15%). A persistent glucose uptake, marker of viability, was mainly seen in risk region (135 +/- 85%) where leukocytes accumulation was moderate in comparison to normal zone (146 +/- 44%). Thus, the glucose uptake observed in viable tissue is mainly related to myocytes metabolism and not to leukocytes metabolism.

Nitrogen-13-ammonia and oxygen-15-water estimates of absolute myocardial perfusion in left ventricular ischemic dysfunction.

UNLABELLED: Measurements of resting myocardial blood flow (MBF) in patients with chronic left ventricular ischemic dysfunction by 15O-water with 13N-ammonia and PET have yielded conflicting results. The aim of this study was to perform a head-to-head comparison of both tracers in the same patient population and to answer the question of whether distinctive tracer properties account for differences in estimates of MBF in chronically dysfunctional myocardium by both tracers. METHODS: A total of 30 patients with chronic dysfunction of the anterior myocardial wall due to significant left anterior descending coronary artery disease underwent PET measurements of absolute MBF in the anterior wall by use of 15O-water and 13N-ammonia before coronary revascularization by either coronary artery bypass graft (n = 24) or percutaneous transluminal coronary angioplasty (n = 6). Improvement of regional contractile function was assessed by two-dimensional echocardiography at a mean of 7.5 +/- 2.1 mo after revascularization. As judged from the changes in anterior myocardial wall motion after revascularization, patients were considered to have either reversibly (n = 16) or persistently (n = 14) dysfunctional myocardium. Estimates of MBF by 15O-water and 13N-ammonia, obtained in every patient before revascularization, were compared among the two patient groups by use of previously validated methods. RESULTS: With 13N-ammonia, resting regional MBF was significantly higher in reversibly as opposed to persistently dysfunctional segments [84 +/- 8 versus 48 +/- 6 ml (min x 100 g)(-1), mean +/- s.e.m., p < 0.01]. By contrast, no such difference was found when using 15O-water to measure MBF [74 +/- 6 versus 86 +/- 9 ml (min x 100 g)(-1), p = ns]. This was mainly due to the fact that the perfusable tissue fraction (PTF), a fitted parameter of the 15O-water model, was significantly higher in reversibly as opposed to persistently dysfunctional segments (0.63 +/- 0.03 versus 0.50 +/- 0.03, p < 0.05). As a consequence, the 15O-water perfusable tissue index (PTI), which is the ratio of the PTF to the anatomical tissue fraction, was greater in reversibly dysfunctional as opposed to persistently dysfunctional segments (1.07 +/- 0.07 versus 0.79 +/- 0.05, p < 0.01). CONCLUSION: This study demonstrates significant differences in MBF estimates between 15O-water and 13N-ammonia in chronically dysfunctional ischemic myocardium. Our results indicate that the 15O-water method yields higher absolute MBF values than the 13N-ammonia approach. Our results also support the use of PTI as a marker of myocardial tissue viability.

Additional myeloablation with 52Fe before bone marrow transplantation.

For many hematological malignancies, high-dose chemoradiotherapy followed by bone marrow transplantation offers the best and sometimes the only chance for cure. However, the main causes of failure of this therapy are relapse and toxicity. In order to selectively deliver higher doses of radiotherapy to the bone marrow and to spare normal organs, we explored 52Fe therapy before a conventional BMT conditioning regimen. Twenty-four patients at high risk for relapse after BMT were included in a phase II study. The median follow-up was 42 months. The median 52Fe dose was 59 mCi. This resulted in a median radiation-absorbed dose (RAD) to the BM of 626 rad. The median RAD to the liver was 338 rad. No untoward effects were noted after the injections of 52Fe. The patients recovered hematopoiesis without toxicity in excess of that expected with conventional conditioning alone. The 3-year DFS probability was 49% (95% CI: 20-78%). Eight patients have relapsed, three of them in extramedullary sites. 52Fe should provide a way to boost the radiation dose to marrow-based diseases before bone marrow transplantation without excessive toxicity.

Brain glucose utilization in childhood Huntington's disease studied with positron emission tomography (PET).

Brain glucose metabolism was measured in two children with early-onset Huntington's disease, using positron emission tomography with fluorodeoxyglucose (FDG) as the tracer. A marked (48%) hypometabolism was found at the level of the caudate nuclei, but other areas of the brain, particularly the cerebral cortex, were not significantly affected. Despite its different clinical presentation, Huntington's disease in children is characterized by brain metabolic alterations similar to those found in adult patients.

[Cerebral glucose metabolism in autistic children. Study and positron emission tomography]. / Métabolisme cérébral du glucose chez les enfants autistes. Etude en tomographie par émission de positrons.

Brain glucose metabolism was measured in 18 autistic children, using high resolution positron emission tomography (PET Scan), with fluorodeoxyglucose (FDG) as tracer. Measurements were performed on an ECAT III tomograph (CTI). Global brain glucose utilization in the autistic population was slightly more elevated than in young adult volunteers, particularly in frontal cortical regions, an observation previously reported for adult autists (Rumsey et al., 1985). However, mean brain glucose metabolism did not differ significantly from that of control children. Regional metabolic maps were also normal, although there was evidence for heterogeneities, particularly at the level of prefrontal and parieto-occipital association areas: 6 children showed a relative hyperfrontality whilst hypofrontality was found in 2 cases. These data suggest that PET might be useful for a better definition of subsets of autistic syndrome in children.

Technetium absorption and turnover in monogastric and polygastric animals.

Technetium (Tc) released into the environment can reach animals in various chemical forms: as pertechnetate (TcO-4) in drinking water or deposited on the surface of vegetables and forage plants, or as Tc bioincorporated into plants and associated with various plant constituents. In addition to being influenced by chemical speciation in the diet, absorption, metabolism, and retention of Tc in animals are modified by the treatment that the alimentary bolus undergoes during its passage through the gastrointestinal tract. This behavior differs markedly between polygastric and monogastric animals. We have, therefore, studied the fate of 99mTc given in the diet either as TcO-4 or bioincorporated into maize in rats (as an example of a monogastric animal) and in sheep (as an example of a polygastric animal). Urine and feces were collected and assayed for Tc activity by gamma spectrometry. Animals were sacrificed at different times after contamination, and the Tc content of tissues was determined. The pattern of absorption, excretion and, to a certain degree, of organ distribution and retention depended on animal species and species of Tc administered. Excretion was by feces and urine, and several metabolic components could be discerned. A component of very short half-time in urine suggests that newly absorbed Tc is more readily excreted than that already bound by tissues. The highest tissue concentrations were found in the thyroid. Retention of Tc was, however, most pronounced in bone and skin. Hair contains considerable amounts of Tc and may serve as a bioindicator of Tc contamination.

Characterization of two mechanisms of (28)Mg uptake in rat jejunal brush border membrane vesicles.

Uptakes of (28)Mg at 10 s were measured at 0.1 and 1mM MgCl(2), to mainly represent one or other of the two uptake mechanisms earlier shown to be present in rat jejunal brush border membrane vesicles, one with an apparent KT of 0.2 mM, the other in the millimolar range. Both mechanisms had an optimal temperature close to 28 degrees C, inactivation at 37 degrees C being more acute for the low affinity mechanism (55 percent, P < 0.01). Both mechanisms were equally stimulated by an electrical potential difference (negative inside the vesicles) imposed by a potassium gradient and not affected by the nature of the anion accompanying magnesium. At 0.1 mM MgCl(2), the uptake was increased by an outwardly directed proton gradient, pH 8.2 outside and 7.4 inside (38 percent, P < 0.05), but not depressed when the gradient was in the opposite direction, pH 6.6 outside and 7.4 inside. It was trans-stimulated by magnesium, strongly inhibited by amiloride and to a smaller extent by furosemide, but uninfluenced by 0.1 mM NaCl or by 100 mM NaCl, NaSCN or KCl. A slight but significant inhibition (20-30 per cent) was recorded in the presence of 0.1 mM CoCl(2), NlCl(2) or BaCl(2). At 1 mM MgCl(2), the uptake was not influenced by pH gradient, was not trans-stimulated by Mg and was not affected by furosemide. A 40 percent inhibition by amiloride was, however, recorded. Also 100 mM NaCl or KCl doubled the uptake, while 1 mM NaCl or 100 mM NaSCN did not affect it. In contrast, all the divalent cations tested produced an inhibition (from 60 to 12 percent) in the following order: Co > or = Mn > Ca > or = Ni> Ba > Sr, when used at the same concentration as magnesium. The results showed that cobalt and calcium were not true competitors. In conclusion, two distinct mechanisms would operate magnesium entry at the brush border: (1) an electrogenic high affinity Mg/Mg,H exchange, sensitive to amiloride and furosemide, and (2) an electrogenic low affinity mechanism, inhibited by the presence of several divalent cations and dependent on the presence or activity of alkaline phosphatase.

Uptake of (28)Mg by duodenal and jejunal brush border membrane vesicles in the rat.

Mg uptake was investigated with (28)Mg by a rapid filtration procedure in rat duodenal and jejunal brush border membrane (BBM) vesicles, prepared by CaCl(2)a or MgCl(2)b differential precipitation. At 1 mM Mg, 10 s uptakes were lower in jejunal vesicles (3.5(a) or 5.5(b) nmol/10 s per mg protein) than in duodenal vesicles (11.4(a) or 13.5(b) nmol/10 s per mg protein). The equilibrated 60 min uptakes were also lower in jejunum (11.0(a) or 26.6(b) nmol/60 min per mg protein) than in duodenum (l8.8(a) or 26.6(b) nmol/60 min per mg protein). The influence of medium osmolarity on 10s and 60 min uptakes of Mg indicated that Mg was 'transported' into osmotically active spaces. The effect of Mg concentration on the 10 s uptake suggested the existence of one single mechanism of transport in the duodenum, with an apparent K(T) of 1 mM, and of two mechanisms in the jejunum, with apparent K(T) values of 0.2 and 2-5 mM. Despite different amounts of calcium and magnesium in CaCl(2) and MgCl(2) precipitated vesicles, there were no large differences in magnesium uptakes depending on the mode of preparation of the vesicles. In contrast, calcium uptakes. measured with (45)Ca, were six to nine times higher in MgCl(2) prepared jejunal vesicles, and were always much higher than magnesium uptakes measured under the same conditions. At 0.1 mM calcium concentration, calcium uptake was depressed by 0.025 mM verapamil (50 percent) and by 0.1 mM ZnCl(2)(40-75 percent), while Mg uptakes were unaffected. L-leucine or L-phenylalanine (5 mM), two inhibitors of intestinal alkaline phosphatase, decreased Mg uptake by 30 to 40 percent at 1 mM Mg, but had no significant effect at 0.1 mM, and did not affect calcium uptakes at all. A possible involvement of alkaline phosphatase in magnesium uptake was ascertained in jejunal BBM vesicles treated with phosphatidylinositol-specific phospholipase C, which partially released alkaline phosphatase from the BBM. Calcium uptakes were unaffected by the treatment, while magnesium uptakes were significantly decreased at 1 mM Mg. These results confirm that magnesium and calcium are transported by distinct mechanisms in the jejunum.

Magnesium uptake by intestinal brush-border membranes of spontaneously hypertensive rats.

Magnesium uptake by intestinal brush-border membranes (BBM) was studied in duodenal and jejunal vesicles of the spontaneously hypertensive rat (SHR) and normotensive control, the Wistar-Kyoto (WKY) rat. In the duodenum, no statistical difference was evidenced between the two types of rats. By contrast, initial rates of magnesium uptake in jejunal vesicles were lower in SHR (5.4 +/- 2.1 nmol/mg protein x 10 sec) in comparison to WKY rats (11.0 +/- 2.5 nmol/mg protein x 10 sec) at a magnesium concentration of 1 mM (P less than 0.01). In jejunal BBM, kinetic analysis of magnesium uptake showed three components in WKY rats, with one being diffusional. In SHR, only two components were seen, with the diffusional one being absent. The two saturable components showed Vmax of 6.5 +/- 1.3 and 26.2 +/- 6.0 nmol/mg protein x 10 sec and apparent Km of 0.22 +/- 0.12 mM and 1.9 +/- 0.4 mM in WKY rats, and Vmax of 10.9 +/- 3.5 and 14.8 +/- 5.9 nmol/mg protein x 10 sec and apparent Km of 0.43 +/- 0.23 mM and 1.3 +/- 0.2 mM in SHR. Only the component with the lowest apparent affinity appeared statistically different in SHR as compared with WKY rats for both Vmax and apparent Km (P less than 0.05). Time course evolution of magnesium uptake in jejunal BBM indicated, by extrapolation at zero time, that 2.5 and 5.1 nmol magnesium/mg protein in SHR and WKY rats, respectively, would be in the bound state. The study of the influence of medium osmolarity on 60-min magnesium uptakes was also indicative of a smaller binding compartment in jejunal BBM of SHR (3.70 and 8.26 nmol/mg protein in SHR and WKY rats, respectively); at the four osmolarities assayed, the 60-min uptakes were significantly lower in SHR as compared with WKY rats (P less than 0.01). From 60-min glucose uptakes, a smaller volume of jejunal BBM vesicles was determined for SHR as compared with WKY rats (0.34 +/- 0.06 and 0.63 +/- 0.17 microliter/mg of protein in SHR and WKY rats respectively, P less than 0.05), this volume being significantly augmented by the presence of 1 mM MgCl2 (0.48 +/- 0.05 and 1.27 +/- 0.02 microliter/mg of protein in SHR and WKY rats respectively, P less than 0.01). These results suggest that magnesium uptake and binding by jejunal BBM are altered in SHR in comparison to WKY rats, implying a possible role of the small intestine in the abnormalities of magnesium metabolism in genetic hypertension.

Magnesium uptake by pancreatic islet cells is modulated by stimulators and inhibitors of the B-cell function.

28Mg2+ uptake by rat islets was measured during incubation with various stimulators or inhibitors of insulin release. D-Glucose induced a dose-dependent increase in 28Mg2+ uptake after 10 min or 120 min. The threshold concentration was around 6 mM and the maximum effect was observed with 15-20 mM glucose. After 120 min 28Mg2+ uptake was also stimulated by the metabolized sugars mannose, N-acetylglucosamine or glyceraldehyde, was unaffected by the non-metabolized or poorly metabolized L-glucose, galactose, 3-O-methylglucose, 2-deoxyglucose, fructose or mannoheptulose and was inhibited by glucosamine. The effect of glucose was markedly impaired by mannoheptulose, glucosamine, aminooxyacetate and NH4Cl, but was only partially decreased by D600 or diazoxide, which were ineffective in a glucose-free medium. Tolbutamide or KCl slightly increased 28Mg2+ uptake. Alanine, leucine alone or with glutamine, and ketoisocaproate also stimulated 28Mg2+ uptake, whereas arginine and lysine decreased it. These changes in 28Mg2+ uptake, brought about by various modifiers of the B-cell function, are thus similar but not identical to the changes in Ca2+ uptake, and are not the consequence of insulin release. The stimulatory effect of glucose requires glucose metabolism by islet cells, but is only partially due to depolarization of the B-cell membrane.

Glucose modulates Mg2+ fluxes in pancreatic islet cells.

Magnesium, the most abundant intracellular divalent cation, is an essential cofactor for many enzyme systems, but it remains unknown as to whether variations in the cytoplasmic concentration of ionized Mg2+ directly control cellular processes. Experiments with adrenal medullary cells made 'leaky' by exposure to high electric fields provided evidence that Mg2+ could influence hormone release not only by competing with Ca2+ for entry into the cell, but also at intracellular sites controlling exocytosis. A similar conclusion was reached for insulin release in a study using isolated rat islets also subjected to high voltage discharges. There is no experimental evidence, however, that physiological stimuli influence Mg2+ movements in intact secretory cells. We report here that 28Mg2+ fluxes in pancreatic islet cells are markedly modified by glucose, the physiological stimulus of insulin release, but not by its non-insulinotropic analogue, 3-O-methylglucose.

Measurement of cerebral blood flow with a bolus of oxygen-15-labelled water: comparison of dynamic and integral methods.

A method is presented for the measurement of cerebral blood flow (CBF) with a bolus of water labelled with oxygen 15. The method, which has been evaluated in normal volunteers, is based on Kety's model, with two additional parameters to account for the difference in the time of tracer arrival in the radial and carotid arteries ("delay") and for dispersion of the tracer in the body and/or blood counting systems. It combines the advantages of: (i) dynamic data collection for estimation of delay and dispersion; (ii) robustness and linearity of CBF estimates with an integral method; and (iii) simplicity of continuous external monitoring of arterial blood radioactivity, particularly with repeated measurements. An optimized protocol is proposed for routine applications in neurological and neurophysiological studies.

Measurement of erythropoiesis using 52Fe.

A method for determining erythropoiesis quantitatively with 52Fe has been applied to 25 patients with anaemia. The data were derived from quantitative scanning of the erythropoietic areas and the measurement of the plasma iron turnover. We have assessed this 52Fe measurement of erythropoiesis by comparing it with total marrow iron turnover studies. Both methods give similar estimates of erythropoiesis except in patients with severe ineffective erythropoiesis and in a patient with significant peripheral haemolysis, when erythropoiesis as measured with the 52Fe technique gave higher results. In these conditions, the estimate of total erythropoiesis might be more reliable using the 52Fe quantitative scanning technique. However, the measurement of erythropoiesis with 52Fe does not distinguish effective from ineffective erythropoiesis and cannot be applied to patients with extramedullary erythropoiesis.

52Fe for additional marrow ablation before bone marrow transplantation.

The effectiveness of bone marrow transplantation (BMT) for malignant blood diseases remains limited by the inability of the preparative regimen to eliminate the disease without causing toxicity to normal organs. We have used 52Fe to deliver radiotherapy selectively to the BM. Fourteen patients with hematologic malignancies received 52Fe before a conventional BMT conditioning regimen. The median 52Fe dose was 58 mCi (range, 32 to 85 mCi). As evaluated by quantitative scanning, the median percentage of 52Fe taken up by the BM was 82% (range, 36% to 90%). This resulted in a median radiation-absorbed dose to the BM of 632 rad (range, 151 to 1,144 rad). The median uptake of 52Fe by the liver was 18% (range, 10% to 64%) and the median radiation-absorbed dose to the liver was 239 rad (range, 82 to 526 rad). The median whole body radiation-absorbed dose was 46 rad (range, 22 to 68 rad). No untoward effects were noted after the injections of 52Fe. The patients recovered hematopoiesis without toxicity in excess of that expected with conventional conditioning alone. The median follow-up was 8 months and three patients have relapsed. 52Fe should provide a way to boost the radiation dose to marrow-based diseases before marrow transplantation without increasing toxicity.

Assessment of bone marrow blood flow using positron emission tomography: no relationship with bone marrow cellularity.

Bone marrow blood flow has been assessed using positron emission tomography and the 15O-labelled carbon dioxide steady-state technique. The measurements were performed at the site of the posterior iliac crest. The bone marrow blood flow was 10.0 ml/min/100 cm3 +/- 3.0 (SD) in normal volunteers. It was markedly increased in patients with polycythaemia vera (26.9 +/- 4.6), chronic granulocytic leukaemia (25.2 +/- 3.9) and myelofibrosis (35.1 +/- 7.3). However, bone marrow blood flow did not differ from normal in patients with aplastic anaemia, chronic haemolysis or chronic lymphocytic leukaemia. There was no relationship between bone marrow cellularity and bone marrow blood flow. The data show that bone marrow blood flow is markedly elevated in polycythaemia vera, myelofibrosis and chronic granulocytic leukaemia and suggest that bone marrow cellularity is not a major factor in regulating bone marrow blood flow.

Quantitative assessment of erythropoiesis in bone marrow expansion areas using 52Fe.

Quantitative 52Fe scans were performed in 180 patients. Expansion of bone marrow was observed in 70. This bone marrow expansion was a nearly constant feature in haemolytic anaemia and in sideroblastic anaemia. It occurred in a third of the patients with myelofibrosis. In patients with polycythaemia rubra vera, expansion was noticed in only two out of seven. Erythropoiesis in expansion areas occurred despite persistence of fat in the iliac crest bone marrow biopsy. It could exist with a slight increase in erythropoiesis and might develop only after a long period of erythropoietic stimulation. Increased marrow activity can take place without erythropoietic expansion in long bones. The fraction of iron uptake in expansion areas did not exceed a third of total marrow iron uptake. With increasing erythropoiesis, the increase in iron uptake in expansion areas was less marked than the increase in the central areas. Erythropoiesis in expansion areas was usually not of major quantitative importance but could nevertheless reach the erythropoiesis of a normal adult.