An inverse association of cardiovascular risk and frontal lobe glucose metabolism.

OBJECTIVE: To investigate associations between vascular risk profile and cerebral glucose metabolism. METHODS: Subjects ranged from normal to having dementia (age >55 years) and underwent neuropsychological testing, MRI, and FDG PET scanning (n = 58). The Framingham Cardiovascular Risk Profile (FCRP) and its individual components were used as covariates in regression analyses with each PET scan using SPM2. RESULTS: Analyses revealed broad areas of the frontal lobe in which higher FCRP was associated with lower normalized glucose metabolism including the superior medial frontal, superior frontal and superior orbital frontal cortex and the ventrolateral prefrontal cortex. Significant associations were predominately found in the left hemisphere. Independent component analyses revealed interesting regions but further confirm the relevance of the integrative measure of coronary risk. CONCLUSIONS: Although the mechanism of this association bears further investigation, this finding provides further evidence that vascular risk factors have malignant effects on the brain, particularly in the prefrontal cortex.

External versus internal approach to the removal of metallic intraocular foreign bodies.

OBJECTIVE: To review the management of metallic intraocular foreign bodies (IOFB) at a single institution and to compare the use of internal and external approaches for their removal. SUBJECTS AND METHODS: A retrospective review was conducted on 70 eyes from 70 patients who underwent surgical removal of a metallic IOFB with either an internal (vitrectomy followed by forceps or internal magnet use) or external approach (large electromagnet) by seven vitreoretinal surgeons at a single institution between 1973 and 1996. Visual acuity and complications occurring with the two approaches were the main outcome measures studied. RESULTS: Overall, patients showed significant improvement in visual acuity following surgical intervention (P < 0.001) despite widely varying surgical techniques. When the authors compared patients treated with an external versus an internal approach they found no statistically significant difference with regard to visual outcome and a trend toward a higher rate of postoperative endophthalmitis in the external approach group. CONCLUSION: Surgical removal of metallic IOFB results in significant visual improvement. The external approach to the removal of magnetic metallic IOFB remains a viable treatment option in select cases.

Delineation of the border zone of ischemic rabbit myocardium by a technetium-labeled nitroimidazole.

Delineation of viable ischemic myocardium is an important problem in nuclear cardiology. To determine the feasibility of using a technetium-labeled nitroimidazole as an indicator of ischemic myocardium at risk of infarction, we characterized the distribution of a 2-nitroimidazole-derivatized PnAO ligand and its 99mTc complex, 99mTcO(PnAO)-1-CH2-(2NI) (BMS-181321) in the ischemic territory of the left anterior descending (LAD) coronary artery of the rabbit. In preliminary experiments, the performance of 14C-deoxyglucose (14C-2DG) and 14C-misonidazole was assessed relative to apparent regional relative myocardial blood flow (rMBF) indicated by 99mTc-teboroxime using double-label autoradiography in the rabbit LAD occlusion model. After demonstrating that 14C-2DG and 14C-misonidazole are selectively retained in the lateral border of the ischemic territory, BMS-181321 was co-injected intravenously, with either 14C-2DG or 14C-misonidazole, 20 min after LAD occlusion. In a separate experiment, 99mTcO(PnAO)-6-CH3, a complex with the same lipophilicity (log k' 0.26 vs. 0.31) as BMS-181321 but which lacks the 2NI moiety, was co-injected with 14C-2DG. After 30 min, the rabbits were sacrificed and 14C/99mTc autoradiograms were obtained from the same tissue sections. The autoradiograms revealed that BMS-181321 was retained with the same microregional distribution as both 14C-2DG and 14C-misonidazole in the border zone of the ischemic LAD territory. The selective retention of BMS-181321 depends on the presence of the nitroimidazole group, since 99mTcO(PnAO)-6-CH3 has a uniformly low myocardial distribution in contrast to the enhanced uptake of co-injected 14C-2DG. These data demonstrate that BMS-181321 is selectively retained in hypoxic myocardium and demarcates the ischemic border zone in a manner similar to 14C-2DG and 14C-misonidazole.

Myocardial kinetics of a putative hypoxic tissue marker, 99mTc-labeled nitroimidazole (BMS-181321), after regional ischemia and reperfusion.

BACKGROUND: A new nitroimidazole complex, 99mTc-propylene amine oxime-1,2-nitroimidazole (BMS-181321), has been developed to allow the positive imaging of hypoxic myocardium by standard gamma camera techniques. METHODS AND RESULTS: To determine the myocardial kinetics of BMS-181321 during myocardial ischemia and reperfusion, seven open-chest swine were prepared according to a model of extracorporeal coronary perfusion in which left ventricular wall thickening (percent end-diastolic thickness) and substrate use in the left anterior descending (LAD) region ([14C]palmitate and [3H]glucose infusions) were determined. Measurements were obtained at baseline, during 40 minutes of ischemia produced by reducing flow in the LAD distribution by 60%, and during 70 minutes of reperfusion. Three aerobic control hearts were also studied in which LAD blood flow was not reduced. Regional coronary circulation was further assessed in all hearts by use of radiolabeled microspheres injected during ischemia. BMS-181321 (20 to 30 mCi) was injected after 30 minutes of ischemia, and its myocardial uptake was assessed by dynamic planar gamma imaging. Ischemia was associated with declines in fatty acid metabolism (15 +/- 11 mumol.h-1.g dry wt-1, mean +/- SEM), systolic wall thickening (20 +/- 6%), and myocardial oxygen consumption (3 +/- 1 mL.min-1.100 g-1) and an increase in exogenous glucose utilization (75 +/- 13 mumol.h-1.g dry wt-1). Systolic wall thickening recovered by only 8 +/- 3% with reperfusion. Initial distribution of BMS-181321 in the aerobic hearts appeared homogeneous. Washout from the ischemic and reperfused LAD bed was slower than the aerobically perfused LAD bed in the control group (t1/2 = 136 +/- 1 versus 80 +/- 1 minutes, P < .05), allowing visualization of the LAD region during reperfusion. Tissue activity of BMS-181321 was inversely related to LAD blood flow during ischemia (r = -.68 +/- .05), and the ratio of BMS-181321 in the LAD region versus normal myocardium was 1.7 +/- 0.2. Control swine lacked regional deposition of the tracer in the normally perfused LAD distribution. CONCLUSIONS: Thus, acute regional ischemia in these studies was visualized as an increase in retention of BMS-181321, suggesting its applicability in the imaging of clinical conditions of myocardial hypoperfusion.

SPECT imaging of ischemic myocardium using a technetium-99m-nitroimidazole ligand.

UNLABELLED: This investigation evaluates the efficacy of a 99mTc-labeled nitroimidazole (BMS-181321) in identifying oxygen-deprived tissue in two canine models of myocardial ischemia. METHODS: For both models (A and B), epicardial microvascular oxygen pressure (mPO2) was monitored by measuring the oxygen-dependent quenching of phosphorescence lifetime of Palladium mesotetra (4-carboxyphenyl) porphine. In Model A (beagles, n = 5), BMS-181321 was administered intravenously and a distal branch of the left anterior descending coronary artery (LAD) was ligated completely 40 sec later. Ten minutes later, the ligature was released establishing tissue reoxygenation. In Model B, flow through the LAD was reduced until the mPO2 was about 2 Torr. After bolus administration of BMS-181321 (50-60 mCi), coronary ischemia was continued for a residence period of up to 4 hr. RESULTS: With Model A, SPECT reconstructions revealed a small ischemic area in three of five dogs, however, a transmural accumulation of the compound was evident in the autoradiograms from all dogs. In the two animals in which the defect was not observed by SPECT, the ischemic episode had nominal effects on the ratio of +/- dp/dt (< 4% change as compared to baseline values). In Model B, SPECT reconstructions showed positive images of the oxygen-deprived area within the mid- to apical regions of the left ventricle (n = 5). Autoradiographic analysis showed a transmural association with cells resulting in an ischemic-to-nonischemic ratio of 3.5 +/- 0.4 (n = 4) for animals with similar residence times. CONCLUSION: The results from both models suggest that BMS-181321 provides a noninvasive marker of regional ischemia in the heart and that this compound may have clinical utility for detection of coronary artery disease.

BATO complexes derived from dimethoxy dioximes: synthesis, characterization and biodistribution.

To prepare less lipophilic BATO complexes, two new methoxy-substituted dioximes were synthesized: cis-4,5-dimethoxycyclohexane-1,2-dione dioxime (DMCDO) and 1,4-dimethoxybutane-2,3-dione dioxime (DMDMG). 99mTcCl(DMCDO)3BMe (BMe = methylboronic acid) was prepared and characterized. Reversed-phase HPLC analyses of 99mTcCl(DMCDO)3BMe and 99mTcCl(DMCDO)3-p-TBA (p-TBA = p - tolylboronic acid) indicated that both of these complexes were mixtures of four enantiomeric pairs of diastereomers. Attempted preparation of a BATO complex from DMDMG gave a mixture of products. In rats, 99mTcCl(DMCDO)3BMe displayed more rapid liver and renal clearance than 99mTcCl(CDO)3BMe, but 99mTcCl(DMCDO)3BMe and 99mTcCl(DMCDO)3-p-TBA displayed low uptake in both heart and brain.

Imaging ischemic tissue at risk of infarction during stroke.

Autoradiograms obtained after middle cerebral artery occlusion (MCAO) in spontaneously hypertensive rats show that the 99mTc complex of a 2-nitroimidazole-derivatized propylene amine oxime (BMS-181321) is selectively retained in acutely ischemic brain before disruption of the blood-brain barrier (BBB), but not in the ischemic infarct. BMS-181321 is therefore a marker of ischemic tissue at risk of infarction and its uptake, unlike that of x-ray and magnetic resonance contrast agents, does not require disruption of the BBB. In keeping with this conclusion, we have found that the single-pass cerebral extraction fraction of BMS-181321 is 0.67 at normal rat whole-brain blood flow. Sequential single-photon emission computed tomographic images obtained from cats after MCAO show that the initial distribution of BMS-181321 approximates regional CBF and that selective retention subsequently produces a positive image within the ischemic territory. BMS-181321 is the first Tc complex able to indicate not only ischemia, but also ischemic tissue at risk of infarction. Use of this novel Tc complex to monitor biochemical events during ischemia may contribute to the clinical management of acute stroke.

The single-pass cerebral extraction and capillary permeability-surface area product of several putative cerebral blood flow imaging agents.

We have determined cerebral blood flow (CBF) and the single-pass cerebral extraction (E) of several putative agents for external imaging of CBF. Simultaneous measurements of blood flow and extraction were performed in 106 rats. For all agents, comparison of linear and exponential regressions of E on CBF indicates that this relationship can be described as linear over the range of flows studied. Analysis of covariance indicates that the extraction of 123I-IMP, 67Cu-PTSM and 99mTc-HMPAO is higher than that of 99mTc-Cl(DMG)3(2MP) and 99mTc-ECD, particularly at flows above the normal range. Accordingly, for 123I-IMP, 67Cu-PTSM and 99mTc-HMPAO, the slope of the linear regression equation for the relationship between brain capillary permeability surface area product (PS) and CBF is higher than that for 99mTc-Cl(DMG)(3)2MP and 99mTc-ECD. PS varies as a linear function of CBF over the range of flows studied. At a CBF level that corresponds to normal regional CBF for human cortex, 0.5 ml/g/min, all the agents have a single-pass extraction of approximately 70% or greater. While all the agents detected changes in CBF in the normal to ischemic range, at higher flows 123I-IMP, 67Cu-PTSM and 99mTc-HMPAO showed substantially greater fidelity to true CBF than 99mTc-Cl(DMG)(3)2MP and 99mTc-ECD.

Measurement of myocardial blood flow using a co-injection technique for technetium-99m-teboroxime, technetium-96-sestamibi and thallium-201.

We have compared apparent myocardial blood flow (MBFapparent) indicated by 99mTc-teboroxime, 96Tc-sestamibi and 201TI to true MBF indicated by radiolabeled microscopheres using a technique for the co-injection of four radionuclides in the same animal. Studies were performed using rats in a single-pass model to obtain global MBF and using dogs in a multiple-pass model to determine regional MBF. To provide a wide range of MBF, adenosine was administered intravenously and the left anterior descending coronary artery was then ligated in the dogs, or hypercapnia was induced by decreasing respiratory frequency in the rats. The microsphere formula for determining MBF was applied to all agents. When MBFapparent was plotted as a function of true MBF, the ability of each agent to measure changes in true MBF was demonstrated by the proximity of the plotted function to the line of identity. For both the single and multiple-pass studies, statistical analysis of the nonlinear relationship between MBFapparent and true MBF showed that 201TI and 99mTc-teboroxime approximate true MBF better than 96Tc-sestamibi (p less than 0.001) under the conditions used in the present studies. In the single-pass studies, 99mTc-teboroxime approximated true MBF better than 201Tl (p less than 0.05), but in the multiple-pass experiments, 201Tl approximated true MBF better than 99mTc-teboroxime in only one dog (p less than 0.01) with no difference in the other two. Determination of the permeability-surface area product, PS, for each agent shows that the higher fidelity to true MBF obtained with 201Tl and 99mTc-teboroxime is related to substantially greater PS values for these agents relative to 96Tc-sestamibi.

'Depletion' of ATP by 2-deoxyglucose: secretion by electroporated human neutrophils is not restored by readdition of ATP.

Studies of intracellular signal transduction are facilitated by the use of permeabilized cell systems, which permit the ready manipulation of the cytosol. These model systems have helped to define the roles that small solutes, particularly Ca2+ and nucleotides, play in stimulus-response coupling. In circumstances where the full depletion of intracellular ATP contents is required, some investigators have resorted to prior treatment with metabolic toxins, with the expectation that the role of ATP in signal transduction could then be more unambiguously studied. However, in the work reported here, we found that treatment with 2-deoxyglucose (2-DOG) irreversibly altered the cells: when poisoned human neutrophils were then permeabilized, the cells failed to degranulate well in response to Ca2+, and their sensitivity to Ca2+ could not be recovered by the readdition of ATP. Inhibition of secretion by 2-DOG was most pronounced when low concentrations of Ca2+ were used as the stimulus. Preincubation of the cells with only 1 mM 2-DOG for 10 min at 37 degrees C (prior to washing and permeabilizing the cells) was sufficient for maximal inhibition. Even without preincubation, high concentrations of 2-DOG directly inhibited secretion. The refractory nature of poisoned cells was not restored by the presence of Mg2+ and/or ATP. The protein kinase C agonist phorbol myristate acetate also did not restore sensitivity of secretion to Ca2+. Addition of ATP and/or GTP to the permeabilization medium (to maximize penetration of the nucleotides) failed to restore sensitivity; tracer studies demonstrated that these conditions were adequate for repletion of the nucleotide pool. These data indicate that human neutrophils poisoned with 2-DOG were irreversibly altered, such that restoration of the putative deficiency (ATP) was without effect. Experiments in which such preincubation measures are employed should be viewed with caution.

Dual effects of guanosine 5'-[gamma-thio]triphosphate on secretion by electroporated human neutrophils.

It is generally believed that G-proteins play stimulatory roles on cell activation. In contrast, we found that guanosine 5'-[gamma-thio]triphosphate (GTP[S]) was a potent inhibitor of Ca(2+)-induced secretion from specific granules (as monitored by vitamin B-12-binding protein). GTP[S] inhibition of specific-granule release occurred in the presence or absence of adenine nucleotides, required Mg2+ (1-3 mM), and was half-maximal at 30 microM-GTP[S]. The dual stimulatory and inhibitory effects of GTP[S] could be readily observed and differentiated when degranulation was monitored over a range of Ca2+ concentrations. Inhibition of specific-granule release by GTP[S] was observed at low Ca2+ concentrations and resulted from shifting the Ca2+ dose-response curves to the right. In contrast, GTP[S] promoted azurophil-granule secretion at relatively high concentrations of Ca2+ and appeared to be due to a general enhancement at all Ca2+ concentrations. A series of hydrolysable and non-hydrolysable nucleotides did not mimic GTP[S] or block its action. Inhibition by GTP[S] occurred in cells which were sensitized with a protein kinase C agonist, suggesting that inhibition of secretion took place distal to this enzyme. However, the inhibitory effects of GTP[S] on specific-granule secretion were reversed by cytochalasin D, which prevents new microfilament formation; this compound also enhanced the stimulation of azurophil-granule release by GTP[S]. We also found that GTP[S] greatly increased the F-actin content of permeabilized neutrophils, whereas Ca2+ (to a lesser extent) decreased F-actin. These data are consistent with the hypothesis that at least two G-proteins are involved in regulating secretion: one which has been previously described as stimulating Ca(2+)-induced secretion (particularly from azurophil granules) and a second, possibly involved in promoting microfilament assembly, which inhibits the discharge of specific granules.

Cyclic AMP inhibits secretion from electroporated human neutrophils.

It has long been known that intracellular cAMP inhibits and cGMP enhances intact neutrophil function. However, these effects are modest and require relatively high concentrations of the cyclic nucleotides. We decided to re-examine the effects of cyclic nucleotides on Ca2(+)-induced secretion by electroporated cells. This system allowed us to bypass normal cell surface receptor-ligand interactions as well as to directly expose the intracellular space to native cyclic nucleotides. We found that concentrations of cAMP as low as 3 microM inhibited Ca2(+)-induced secretion; 30-300 microM cAMP was maximally inhibitory. cAMP was actually slightly more potent than dibutyryl cAMP, a membrane-permeant derivative. In contrast, cGMP was only slightly stimulatory at 3 microM and modestly inhibitory at 300 microM; dibutyryl cGMP was ineffective. A more detailed investigation of the effects of cAMP showed that inhibition was only obtained in the presence of Mg2+. Half-maximal inhibition by cAMP occurred at 10-30 microM. Inhibition by cAMP was achieved by shifting the Ca2+ dose-response curve for secretion to the right; this was observed for the release of both specific granules (vitamin B12 binding protein) and azurophil granules (B-glucuronidase). We previously showed that ATP could enhance Ca2(+)-induced secretion in the presence of Mg2+, apparently by interacting with a cell surface purine receptor. However, increasing concentrations of ATP could not overcome inhibition by cAMP; this suggested that cAMP acted at some site other than the purine receptor. Inhibition by cAMP was also less apparent in the presence of the protein kinase C agonist phorbol myristate acetate (PMA), suggesting that the cyclic nucleotide did not produce systemic desensitization of the neutrophils. In summary, these results demonstrate that low, physiologically relevant concentrations of cAMP can modulate neutrophil responsiveness.

A neutral lipophilic technetium-99m complex for regional cerebral blood flow imaging.

Technetium-99m-DMG-2MP (Chloro[bis[2,3-butanedionedioxime(1-)-0][2,3- butanedionedioximato (2-)-N,N',N'',N''',N'''',N'''''] (2-methylpropyl borato (2-))technetium]), also known as SQ 32097 is a member of a family of neutral lipophilic compounds generally known as boronic acid adducts of technetium dioxime complexes (BATOs). After i.v. administration, the concentration of [99mTc]DMG-2MP in various regions of the brain appears to be proportional to blood flow. In rats, 1.1% ID was in the brain at 5 min postinjection when the blood contained less than 3% ID. Over 24 hr excretion was 59% in the feces and 23% in the urine. The activity in monkey brain at 5 min was 2.8% ID and it cleared with a t1/2 of 86 min. Autoradiographs of monkey brain sections showed excellent regional detail with a gray/white ratio of 3.6 at 10 min. The distribution of [99mTc]DMG-2MP in the monkey brain corresponds to the known cytoarchitectural pattern of cerebral glucose metabolism. The properties of [99mTc]DMG-2MP make it a potentially useful agent for cerebral perfusion imaging in man.

A neutral technetium-99m complex for myocardial imaging.

Technetium-99m-CDO-MeB [Bis[1,2-cyclohexanedione-dioximato(1-)- O]-[1,2-cyclohexanedione dioximato(2-)-O]methyl-borato(2-)- N,N',N'',N''',N'''',N''''')-chlorotechnetium) belongs to a family of compounds generally known as boronic acid adducts of technetium dioxime complexes (BATOs). It has an intrinsic affinity for the myocardium, with negligible lung activity and rapid blood clearance. The uptake of 3.44% ID in rat heart at 1 min postinjection for [99mTc]CDO-MeB versus 3.03% for 201TI indicates high extraction of [99mTc]CDO-MeB by the myocardium. In dogs an ischemic defect is clearly seen in SPECT images obtained 10 min after injection of [99mTc]CDO-MeB. Tissue distribution data in rats show that [99mTc]CDO-MeB is excreted primarily in the feces and to a lesser extent in the urine. Approximately 80% of the activity is excreted within 24 hr after injection.

[Effect of exercise therapy on the PH, pO2 and pCO2 of capillary blood of centrally paralyzed limbs after stroke]. / Wplyw kineziterapii na pH, pO2 i pCO2 w krawi wlosniczkowej konczyn centralnie porazonych u chorych po udarze mózgu.

Gasometric determinations of pO2, pCO2 and pH were carried out in capillary blood obtained from the upper extremities before and after 10 minutes of kinesitherapy in 30 patients with hemiplegia following stroke. The determinations were done with an acid-base equilibrium analyser Radiometer Copenhagen pH M 71 MKZ. Ten minutes of kinesitherapy caused significant changes in the pH of the blood towards alkalinization, less pronounced in the paralytic extremities. However, differences in the determinations in paralytic and non-paralytic extremities were statistically not significant. These results confirm earlier observations of the authors and point out that 10 minutes of kinesitherapy seems to be the shortest times of exercise giving significant biochemical and clinical effect.