Multi-ancestry Genome-Wide Association Study of Early Childhood Caries.

Early childhood caries (ECC) is the most common non-communicable childhood disease. It is an important health problem with known environmental and social/behavioral influences that lacks evidence for specific associated genetic risk loci. To address this knowledge gap, we conducted a genome-wide association study of ECC in a multi-ancestry population of U.S. preschool-age children (n=6,103) participating in a community-based epidemiologic study of early childhood oral health. Calibrated examiners used ICDAS criteria to measure ECC with the primary trait using the dmfs index with decay classified as macroscopic enamel loss (ICDAS ≥3). We estimated heritability, concordance rates, and conducted genome-wide association analyses to estimate overall genetic effects; the effects stratified by sex, household water fluoride, and dietary sugar; and leveraged the combined gene/gene-environment effects using the 2-degree-of-freedom (2df) joint test. The common genetic variants explained 24% of the phenotypic variance (heritability) of the primary ECC trait and the concordance rate was higher with a higher degree of relatedness. We identified 21 novel non-overlapping genome-wide significant loci for ECC. Two loci, namely RP11-856F16 . 2 (rs74606067) and SLC41A3 (rs71327750) showed evidence of association with dental caries in external cohorts, namely the GLIDE consortium adult cohort (n=∼487,000) and the GLIDE pediatric cohort (n=19,000), respectively. The gene-based tests identified TAAR6 as a genome-wide significant gene. Implicated genes have relevant biological functions including roles in tooth development and taste. These novel associations expand the genomics knowledge base for this common childhood disease and underscore the importance of accounting for sex and pertinent environmental exposures in genetic investigations of oral health.

Pseudonocardia babensis sp. nov., isolated from plant litter.

A novel actinomycete, designated strain VN05A0561(T), was isolated from plant litter collected at Ba Be National Park, Vietnam. The substrate mycelia and spore chains fragmented in a manner similar to nocardioform actinomycetes; the spores had smooth surfaces and were rod-shaped. Strain VN05A0561(T) had the following chemotaxonomic characteristics: meso-diaminopimelic acid in the cell-wall peptidoglycan, arabinose and galactose as characteristic sugars, MK-8(H4) as the major isoprenoid quinone, phosphatidylcholine as the diagnostic phospholipid and iso-C16:0 as the major cellular fatty acid. Strain VN05A0561(T) shared low levels of 16S rRNA gene sequence similarity (< 97 %) with the type strains of recognized species of the genus Pseudonocardia and could be differentiated from its closest phylogenetic relatives based on phenotypic characteristics. These results suggested that strain VN05A0561(T) represents a novel species of the genus Pseudonocardia, for which the name Pseudonocardia babensis sp. nov. is proposed. The type strain is VN05A0561(T) (=VTCC-A-1757(T)=NBRC 105793(T)).

Kineosporia babensis sp. nov., isolated from plant litter in Vietnam.

Three actinomycetes, designated strains VN05A0342, VN05A0351 and VN05A0415(T), were isolated from plant-litter samples collected in the north of Vietnam and examined in a polyphasic taxonomic study. Phylogenetic analysis based on the 16S rRNA gene sequences showed that these isolates were most closely related to the type strain of Kineosporia mikuniensis (98.5 % sequence similarity). Morphological properties (the formation of spore domes and motile spores) and chemotaxonomic data supported the assignment of the three isolates to the genus Kineosporia. The isolates all contained the following: meso-diaminopimelic acid in the peptidoglycan (with small amounts of the ll isomer); ribose, mannose, galactose and glucose as the whole-cell sugars; MK-9(H(4)) as the predominant isoprenoid quinone; C(18 : 1) and C(16 : 0) as the major cellular fatty acids; and phosphatidylcholine, phosphatidylglycerol, diphosphatidylglycerol and phosphatidylinositol as the phospholipids. The high DNA-DNA relatedness (>71 %) among the three isolates showed that they represented a single species. On the other hand, the DNA-DNA relatedness between the novel isolates and all type strains of Kineosporia species was less than 46 %. The physiological properties of our isolates were distinct from those of all of the Kineosporia species with validly published names, e.g. decomposition of l-tyrosine and aesculin and the utilization of raffinose and d-arabitol. Therefore, strains VN05A0342, VN05A0351 and VN05A0415(T) represent a novel species of the genus Kineosporia, for which the name Kineosporia babensis sp. nov. is proposed. The type strain is VN05A0415(T) (=VTCC-A-0961(T) =NBRC 104154(T)).

Quantitative imaging of gene induction in living animals.

Methods to repeatedly, non-invasively, and quantitatively image gene expression in living animals are rapidly emerging and should fundamentally change studies of gene expression in vivo. We previously developed assays utilizing positron emission tomography (PET) to image reporter gene expression. In this paper we: (1) describe a new bi-directional, tetracycline-inducible system that can be used to pharmacologically induce target gene expression and to quantitatively image induced expression by using a PET reporter gene; (2) demonstrate the potential of this system in transient and stable cell transfection assays; and (3) demonstrate the ability to repetitively and quantitatively image tetracycline and tetracycline analog induction of gene expression in living animals. We utilize the dopamine type-2 receptor (D(2)R) and the mutant herpes-simplex virus type 1 thymidine kinase (HSV1-sr39tk) reporter genes to validate this system. We utilize microPET technology to show that quantitative tomographic imaging of gene induction is possible. We find a high correlation (r(2) = 0.98) between 'target' and reporter gene expression. This work establishes a new technique for imaging time-dependent variation of gene expression both from vectors with inducible promoters and in transgenic animals in which pharmacologic induction of gene expression must be monitored. These techniques may be applied both in gene therapy and for the study of gene expression in transgenic animals.

Post-injection delays in experimental chambers, but not in home cages, produce both sensitization and tolerance of operant behaviour to midazolam: relation to pharmacokinetics.

The effects of post-injection delay time and environmental context on behaviour after subcutaneous administration of 3 mg/kg midazolam were investigated under a differential reinforcement of low rate schedule (i.e. DRL 45 s) in 3 h sessions. Post-injection delays were varied (0-120 min) for two groups of rats placed in either the experimental chamber (group 1) or home cage (group 2) during the pre-session delay times. Midazolam increased shorter-response (inter-response times < 45 s) rates and decreased reinforcement rates in a time-related manner. Reinforcement rate-time profiles were also integrated with parallel pharmacokinetics. Post-injection delays in either environment yielded performances that mirrored the pharmacokinetic profile operative at the corresponding time-delay points. At higher concentrations (> 0.12 microg/ml) the pharmacokinetics of midazolam largely determined the behavioural effects in both groups, regardless of post-injection delays. However, at lower drug concentrations, longer post-injection delays (> 60 min) in the experimental chamber produced both sensitization and tolerance, as measured by greater increases in shorter-response rates and a more rapid return of the reinforcement rate, respectively. Interaction of the discriminative stimulus effects of midazolam with the context probably alters the magnitude of behavioural effects when the delay occurs in the experimental chambers, whereas no such interaction is present in group 2. The DRL schedule with post-injection delays in experimental chambers provides a useful behavioural paradigm for studying both sensitization and tolerance.

Pharmacokinetic determinants of cocaine's differential effects on locomotor and operant behavior.

Dose-response, effect-time and concentration-effect relations of intravenous cocaine (1-4 mg/kg) were investigated on contingency-controlled [fixed-ratio (FR) 70 performance] and unconditioned (locomotor activity) behaviors. Cocaine dose-response curves exhibited decreasing rates of response under the FR 70 schedule but increasing locomotor activity in a dose-related fashion. Effect-time profiles confirmed that these changes were time-dependent and provided additional clarity by mirroring the biexponential decay of cocaine concentrations with time. The duration of action of cocaine was comparatively shorter on locomotor activity than on FR performance. We integrated effect-time profiles of the two behaviors with concentration-time profiles simulated from our previously published pharmacokinetic parameters to derive cocaine's pharmacodynamic parameters. Classical inhibitory Emax and sigmoidal Emax models were used to describe cocaine's effects on FR performance and locomotor activity, respectively. Simultaneous pharmacokinetic-pharmacodynamic modeling reveals evidence of acute tolerance to cocaine in locomotor activity, as indicated by decreasing potency with dose, but not in contingency-controlled behavior.

HL-91-technetium-99m: a new marker of viability in ischemic myocardium.

BACKGROUND: Technetium 99m-HL91 is a new hypoxia imaging agent that demonstrates increased uptake in ischemic, viable myocardium. This study was performed to determine whether HL91 is taken up by nonviable myocardium. METHODS: Twenty-three Krebs-Henseleit buffer-perfused, isolated rat hearts were studied. Tc-99m-HL91 300 microCi was infused over 10 minutes, followed by a 60-minute clearance. Myocardial activity was monitored by use of an NaI crystal. Four groups were studied: control (flow = 12 mL/min, n = 7), low flow (flow = 1 mL/min, n = 6), no flow/reflow (60 minutes no flow/60 minutes reflow before Tc-99m-HL91 infusion, flow = 12 mL/min, n = 5), and cyanide-treated (before Tc-99m-HL91 infusion, flow = 12 mL/min, n = 5). Injury was assessed by creatine kinase, transmission electron microscopy, and triphenyltetrazolium chloride. RESULTS: Control (no injury) and cyanide-treated (severe injury) hearts demonstrated low uptake (6.3+/-0.5 mean+/-SEM and 5.7+/-1.2 microCi, respectively) and low 60-minute retention (13.8%+/-2.2% and 13.7%+/-3.9%, respectively). Low-flow hearts (minimal injury) demonstrated markedly increased uptake (43.5+/-2.8 microCi, P < .01) and increased 60-minute retention (33.2%+/-2.9%, P < .01) compared with control. No-flow/reflow hearts (moderate injury) demonstrated intermediate uptake (8.7+/-0.5 microCi, P < .05 to control), although retention was not significantly different (18.9%+/-3.5%, P = ns). Severely and rapidly injured myocardium demonstrated Tc-99m-HL91 peak uptake and retention indistinguishable from normal. Moderately injured myocardium demonstrated uptake intermediate between severely injured and low-flow-induced ischemic, viable myocardium. CONCLUSION: Thus Tc-99m-HL91 is not taken up or retained in nonviable and irreversibly injured myocardium.

99mTc-HL91: "hot spot" detection of ischemic myocardium in vivo by gamma camera imaging.

BACKGROUND: 99mTc-HL91 is a new hypoxia imaging agent that demonstrates increased uptake and retention in globally hypoxic myocardium in vitro. The purpose of this study was to determine whether 99mTc-HL91 could detect regional ischemia in vivo by gamma camera imaging. METHODS AND RESULTS: Eight open-chest dogs with left circumflex (LCx) stenoses were studied. Injection of 5 mCi of 99mTc-HL91 and microspheres was followed by imaging over 4 hours. Heart slices were imaged, then stained with triphenyltetrazolium chloride (TTC), and tissues were well-counted. TTC staining demonstrated no injury. Mean LCx blood flow was 0.32+/-0.04 mL x min(-1) x g(-1), and mean left anterior descending coronary artery (LAD) flow was 0.96+/-0.02 mL x min(-1) x g(-1) (ratio, 0.33). "Hot spots" were detected in 8 of 8 experiments in vivo within 60 minutes and improved over 4 hours. Region of interest analysis of LCx/LAD activity ratios demonstrated significant increases within 30 minutes (final ratio, 3.0; P<0.05). LCx and LAD washout curves demonstrated significant differences within 15 minutes. Washout curves were biexponential over 1 hour, followed by linear retention from 1 to 4 hours. Four-hour fractional retention was 0.12 for LAD and 0.44 for LCx (P<0.01). Myocardial flow versus tracer uptake demonstrated 2 phases: phase 1 (flow, 0.05 to 0.7 mL x min(-1) x g(-1)) had an inverse linear correlation (r= -0.80); phase 2, (flow, >0.7 mL x min(-1) x g(-1)) had no correlation. Ischemic heart/liver ratios remained near 1.0 for 4 hours. CONCLUSIONS: 99mTc-HL91 positively identifies regional myocardial ischemia in a canine model using 99mTc imaging. Quantitative techniques allowed identification of ischemic myocardium within 15 minutes of tracer administration.

Technetium 99m-HL-91: a potential new marker of myocardial viability assessed by nuclear imaging early after reperfusion.

OBJECTIVE: 99mTc-HL-91 (Prognox) is a potential new hypoxia-avid myocardial imaging agent. The purpose of this study was to determine whether this tracer would demonstrate increased activity in nonviable myocardium in vivo. METHODS AND RESULTS: A 3-hour left circumflex artery (LCx) occlusion was followed by 1 hour of reperfusion, injection of 99mTc-HL-91 (185 MBq), and 2 hours of gamma camera imaging in 6 open-chest canine experiments. Microspheres were injected during baseline, at occlusion, at the time of tracer injection, and at the end of the experiment. After the animals were killed, heart slices were imaged. Blood flow and tracer activity were determined by well counting. Mean infarct size was 19.2% +/- 2.2% (SEM). All six dogs demonstrated no increased 99mTc-HL-91 myocardial activity other than small foci on in vivo and ex vivo gamma camera images. The mean large region of interest (ROI)-determined LCx/LAD (left anterior descending) ratio was 1.10 +/- 0.03 in vivo, and 1.0 +/- 0.02 ex vivo. Mean clearance curves from LCx and LAD ROI were not significantly different, and 2-hour retention was 15.2% +/- 2.1% for the LCx and 18.6% +/- 2.7% for the LAD (p = NS). ROI clearance curves demonstrated biexponential clearance over the first hour and linear clearance over the second hour. Myocardial blood flow (microspheres) versus well-counted tracer uptake curves were linear with near-zero slopes for viable tissue, nonviable tissue, and mosaic tissue. Blood clearance was triexponential with a 2-hour retention of 7.8% +/- 1.1%. CONCLUSIONS: In contrast to viable ischemic tissue, normal and nonviable myocardium demonstrate similar 99mTc-HL-91 uptake and retention kinetics. This agent warrants further clinical studies in situations where there is a need to differentiate ischemic viable from nonviable myocardium.

Comparison of Technetium-99m sestamibi and indium-111 octreotide imaging in a patient with Ewing's sarcoma before and after stem cell transplantation.

BACKGROUND: We report the use of two novel nuclide agents, Technetium-99m (99Tc)sestamibi (MIBI) and indium-111 (In-111) octreotide, in comparison with conventional computed tomography (CT) imaging in a patient with metastatic Ewing's sarcoma (ES) before and after high dose chemotherapy with autologous peripheral stem cell transplantation (PSCT). MIBI is taken up actively by metabolically active tumor cells. Octreotide, a somatostatin analog, binds specifically to somatostatin receptors. METHODS: The patient was a 20-year-old male with recurrent metastatic ES to the lung. Before and sequentially after high dose chemotherapy and PSCT, the patient was imaged with MIBI. Whole body planar and single photon emission computed tomography (SPECT) images were obtained after the injection of 30 mCi of 99Tc MIBI. Prior to PSCT the patient was imaged with 6 mCi In-111 pentreotide. RESULTS: Conventional CT scans also were performed. Initial CT revealed pulmonary metastasis in the right lower lobe along with multiple left pleural-based lesions. These lesions were visualized clearly with MIBI. Octreotide detected only the left lung involvement. Sequential MIBI scans after PSCT correlated with tumor reduction in the right lung field and tumor progression in the left lung as well as the development of new pulmonary metastasis. These findings were confirmed on CT. CONCLUSIONS: MIBI imaging was highly concordant with CT scanning in the detection of metastatic ES. MIBI scanning holds promise for the direct detection of a variety of human malignancies, and may prove useful as a rapid whole body imaging modality.

Planar imaging of 99mTc-labeled (bis(N-ethoxy, N-ethyl dithiocarbamato) nitrido technetium[V]) can detect resting ischemia.

BACKGROUND: (99m)Tc-labeled (bis(N-ethoxy, N-ethyl dithiocarbamato) nitrido technetium(V)) ([99m]TcN-NOET) is a new lipophilic, neutral-charge cardiac perfusion imaging agent that demonstrates apparent redistribution in animal models and humans. The purpose of this study was to determine whether the kinetics of (99m)TcN-NOET are suitable for the detection of resting ischemia. METHODS AND RESULTS: Microspheres were injected at baseline and simultaneously with (99m)TcN-NOET after a 90% reduction in resting flow in the left circumflex coronary artery in six open-chest canine experiments. The relationship of flow and activity early after injection was determined in one experiment by termination at 10 minutes. The flow ratio (left circumflex/left anterior descending coronary artery) after stenosis fell significantly (0.87 +/- 0.04 vs 0.46 +/- 0.04; p < 0.05). The end-tissue (99m)Tc ratio (0.78 +/- 0.05) was significantly higher than the flow ratio at injection (0.46 +/- 0.04; p < 0.05), indicating substantial redistribution. In vivo imaging was conducted during 2 hours in five experiments, followed by ex vivo imaging. Myocardial clearance from 10 minutes onward was biphasic in left anterior descending and monophasic in left circumflex coronary arteries. Myocardial clearance from 10 to 60 minutes was delayed in left circumflex (35.5% +/- 8.1%) versus left anterior descending coronary arteries (49.2% +/- 8.6%; p < 0.05). No significant difference was observed from 60- to 120-minute clearance. Five of five experiments demonstrated initial defects and complete fill-in at 90 to 120 minutes by qualitative assessment. Quantitation of ex vivo images confirmed significant redistribution. CONCLUSIONS: Resting ischemia caused by moderate to severe stenosis can be detected on scans with (99m)TcN-NOET. Redistribution was near complete in this model by 90 to 120 minutes. (99m)TcN-NOET is a promising new agent for the detection of coronary artery disease in viable myocardium and warrants further investigation.

99mTc-HL91. Effects of low flow and hypoxia on a new ischemia-avid myocardial imaging agent.

BACKGROUND: 99mTc-HL91 is a potential imaging agent that has demonstrated increased uptake in hypoxic tumor cells. The purpose of this study was to determine if 99mTc-HL91 demonstrates increased uptake and retention in ischemic and hypoxic myocardium. METHODS AND RESULTS: 99mTc-HL91 (11.1 MBq) was infused over 10 minutes, followed by a 60-minute clearance phase. Activity was monitored by using an NaI detector. Three groups were studied using Krebs-Henseleit buffer (KH): controls (12 mL/min, n = 6), low-flow ischemic (1 mL/min, n = 7), and hypoxic (12 mL/min, n = 8). Two groups were perfused with KH, red blood cells, and albumin: controls (6 mL/min, n = 6) and low-flow ischemic (0.5 mL/min, n = 6). For the KH hearts, the 99mTc-HL91 peak uptake progressively increased from control (6.3 +/- 0.5 microCi, mean +/- SEM) to hypoxic (9.1 +/- 1.0 microCi) to low flow (44.0 +/- 2.6 microCi; P < .01). The peak uptake low-flow/control ratio was 7:1. Final retention increased progressively from control (0.8 +/- 0.1 microCi) to hypoxic (2.9 +/- 0.5 muCi) to low flow (10.9 +/- 1.3 microCi; P < .01). The final low-flow/control activity ratio was 13.6:1. Similar results were observed in the red blood cell-perfused control and low-flow groups. CONCLUSIONS: This study introduces a new myocardial "hot spot" imaging agent, 99mTc-HL91. This agent demonstrates increased myocardial uptake and retention in hypoxic and low-flow ischemic models. Further in vivo imaging studies are warranted to determine the clinical potential of this agent.

Interaction of technetium-99m-N-NOET with blood elements: potential mechanism of myocardial redistribution.

UNLABELLED: Technetium-99m-N-NOET is a new 99mTc-labeled, neutral cardiac perfusion imaging agent which has been shown to undergo apparent redistribution in animal models and in humans. The purpose of this study was to investigate the interaction of 99mTcN-NOET with red blood cells (RBCs) and to determine the effects of these interactions on myocardial uptake and clearance of 99mTcN-NOET. METHODS: After bolus administration, myocardial 99mTcN-NOET clearance was monitored for 1 hr using a sodium iodide detector in 22 isolated, buffer-perfused rat hearts. Hearts were perfused as follows: seven controls with Krebs-Henseleit (KH) buffer (Group 1), five hearts with KH containing RBCs (Group 2), five hearts with KH containing RBCs and albumin (Group 3), five hearts with KH containing RBCs and dextran (Group 4). In a separate protocol, RBCs were incubated in 99mTcN-NOET and then perfused through five hearts (Group 5). RESULTS: Technetium-99m-N-NOET myocardial uptake (%ID) was significantly lower in all RBC groups (RBCs = 5.0% +/- 1.7%; RBCs + albumin = 8.2% +/- 2.1%; RBCs + dextran = 4.0% +/- 0.8%; incubated RBCs = 8.8% +/- 1.5%) compared with controls (72.2% +/- 2.8%; p < 0.05). Retention (99.4% +/- 0.6%) was near linear in the KH control group with virtually no fractional clearance at 60 min. Retention in groups whose perfusates contained RBCs (RBCs = 62.2 +/- 4.2%; RBCs + albumin = 29.9 +/- 4.3%; RBCs + dextran = 69.3 +/- 3.6%) were all significantly lower than control. Addition of albumin to RBC perfusate resulted in significantly lower retention (29.9% +/- 4.3%; p < 0.01) than was observed in RBC perfusate alone (62.2% +/- 4.2%). Substitution of dextran for albumin produced retention similar to RBCs alone (69.3% +/- 3.6%; p = ns). In a separate protocol, RBC binding of 99mTcN-NOET was high (64.4% +/- 8.6%) in triple-washed RBCs. Technetium-99m-N-NOET bound to RBCs was subsequently extracted from red cells by the myocardium when those cells were infused into hearts. CONCLUSION: Technetium-99m-N-NOET has high binding affinity to blood elements and transfers bidirectionally between myocardium and blood. The interaction of 99mTcN-NOET with blood elements represents a potential mechanism of redistribution.

Interaction between enalapril and aspirin on mortality after acute myocardial infarction: subgroup analysis of the Cooperative New Scandinavian Enalapril Survival Study II (CONSENSUS II)

The use of angiotensin-converting enzyme (ACE) inhibitors early after an acute myocardial infarction to reduce mortality has been studied in several trials with inconsistent results. Aspirin (ASA) has become a well-documented therapeutic adjunct in patients with coronary heart disease. Attention has recently been focused on a possible interaction between ASA and ACE inhibitors. We therefore reanalyzed data from the Cooperative New Scandinavian Enalapril Survival Study II (CONSENSUS II) to find any evidence of differential effects of the ACE inhibitor enalapril in subgroups defined by use of ASA at baseline. Logistic regression tested the multiplicative interaction. We used Rothman synergy index S, which would be equal to unity under additivity, and less than unity when suggesting antagonism, to examine the postulated interaction with departure from an additive model. Logistic regression showed that the enalapril-ASA interaction term was a significant predictor of mortality at the end of the study (p = 0.047), and was a borderline significant predictor of mortality 30 days after randomization (p = 0.085). The Rothman synergy index S was 0.66 (95% confidence interval 0.46 to 0.94) for mortality at the end of the study, and 0.68 ( 0.44 to 1.04) for 30-day mortality, indicating antagonism between enalapril and ASA with departure from an additive model. Thus, we found evidence of enalapril-ASA interaction. The effect of enalapril was less favorable among patients taking ASA than among patients not taking ASA at baseline.

Technetium 99m-Q12 kinetics in perfused rat myocardium: effects of hypoxia and low flow.

Technetium 99m-Q12 is a new cationic myocardial perfusion imaging agent that produces excellent images in human beings. The purpose of this study was to examine the separate effects of hypoxia and low flow on myocardial clearance kinetics. After a 1 mCi bolus injection, myocardial 99mTc-Q12 clearance was monitored for 1 hour by using an Nal detector in 24 isolated perfused rat hearts. In 6 control hearts, flow was 12 ml/min, and oxygenation was normal. In 6 hypoxic hearts, flow was normal, but oxygenation was reduced (<5% 02). In 6 low-flow hearts, flow was 3 ml/min, and oxygenation was normal. In 6 very low flow hearts, flow was 1 ml/min, and oxygenation was normal. 99mTc-Q12 myocardial clearance was biphasic in all four groups, consisting of a rapid early phase and a second slow phase that began after 10 minutes. Myocardial retention between 1 and 10 minutes was 56.8% +/- 1.8% for control, 49.2% +/- 2.2% (p < 0.05 compared with control) for hypoxic, 56.8% +/- 2.6% (p = NS compared with control) for low flow (3 ml/min), and 63.7% +/- 2.1 % (p < 0.05 compared with control) for very low flow hearts (1 ml/min). Myocardial retention between 10 and 60 minutes was 90.5% +/- 0.2% for control, 90.2% +/- 1.6% for hypoxic, 90.0% +/- 0.8% for low-flow hearts (3 ml/min), and 87.6% +/- 0.3% (p < 0.05 compared with other groups) for very low flow hearts (1 ml/min). In conclusion, 99mTc-012 demonstrates biphasic clearance from normal, hypoxic, low-flow, and very low flow ischemic myocardium. Early-phase myocardial retention is decreased by hypoxia and increased by very low flow.

Effects of low flow and hypoxia on myocardial retention of technetium-99m BMS181321.

The purpose of the present study was to determine whether graded levels of low-flow ischemia would lead to graded differences in uptake and clearance of BMS181321. Using a perfused rat heart model, 7.4 MBq (200 microCi) of BMS181321 was infused over 20 min, followed by a 60-min clearance phase. Activity was monitored using an NaI detector. Four groups were studied using Krebs-Henseleit buffer perfusion using low flow or hypoxia: group 1=12 ml/min, group 2=3 ml/min, and group 3=1 ml/min during uptake and clearance phases, and group 4=12 ml/min with hypoxia during clearance. Control and low-flow groups were also perfused using red blood cells and albumin. There was a stepwise increase in peak myocardial uptake (% injected dose) as flow progressively decreased (group 1=2.4%+/-0.2% SEM, group 2=13.1%+/-0.7%, group 3=28.6%+/-2.4%, P <0.05). Group 3/group 1 mean peak activity ratio was 12:1. Mean 1-h fractional retention significantly increased in a stepwise manner as flow decreased (group 1=0.32+/-0.02, group 2=0.43+/-0.03, group 3=0.59+/-0.05, P <0.05). Group 3/group 1 mean 1-h clearance activity ratio was 30:1. Groups 5 and 6 perfused with red blood cells and albumin demonstrated similar increases in peak uptake and 1-h retention in the low-flow hearts. This study demonstrates a stepwise increase in uptake and a stepwise increase in retention rate of BMS181321 with progressive reduction in flow.

[Can vitamin E prevent development of coronary heart disease?]. / Kan vitamin E forebygge utvikling av koronar hjertesykdom?

Oxidation of low-density lipoprotein (LDL) probably plays an important part in atherosclerosis. Vitamin E (alpha-tocopherol) is a potent antioxidant carried in LDL. It increases the resistance of LDL to oxidation, thereby, among other things, inhibiting foam cell formation and proliferation of smooth muscle cells. Some animal experiments have indicated that vitamin E retards the development of atherosclerotic lesions. Observational studies (case-control and cohort) have shown that long-term treatment with vitamin E is associated with lower incidence of coronary heart disease in men and women alike. Randomisation to vitamin E in a large placebo controlled trial gave a nonsignificant reduction in mortality from ischemic heart disease. Although vitamin E seems to reduce the risk of coronary heart disease, randomised trials of adequate size are necessary in both secondary and primary prevention in order to test this. Such trials are in progress.

Clearance of technetium 99m N-NOET in normal, ischemic-reperfused, and membrane-disrupted myocardium.

BACKGROUND: Technetium 99m-labeled bis(N-ethoxy, N-ethyl dithiocarbamato) nitrido technetium(v) (99mTcN-NOET) is a new neutral cardiac perfusion imaging agent that has been shown to have very high uptake and retention in vitro. The purpose of this study was to determine the clearance kinetics of 99mTcN-NOET in control, ischemic-reperfused, and membrane-disrupted myocardium. METHODS AND RESULTS: After a 100 microCi (3.7 x 10(6) Bq) bolus of 99mTcN-NOET was injected, myocardial clearance was monitored for 1 hour by the use of a sodium iodide detector in 30 isolated, Krebs-Henseleit (KH) perfused rat hearts. Seven hearts were used as controls (group 1). In seven ischemic-reperfused hearts, tracer administration and uptake was followed by 30 minutes of no flow and 1 hour of reflow (group 2). In six additional ischemic-reperfused hearts, tracer administration was followed by deprivation of flow for 1 hour followed by 1 hour of reflow (group 3). Six hearts were perfused with a 0.5% Triton X-100 KH perfusate for 1 hour (group 4). Four hearts were perfused with KH for 10 minutes, followed by cyanide for 10 minutes (group 5). This cycle was repeated three times. Activities remaining in each heart at the end of each experiment were quantitated, and activity at peak uptake was calculated. The 99mTcN-NOET myocardial clearance was near linear in the control (0.6 +/- 0.4) and both ischemic-reperfused groups with virtually no fractional clearance (1.2% +/- 0.6% and 2.1% +/- 0.6%, respectively; p = NS). In the Triton X-100 membrane-disrupted hearts, clearance was substantial (94.2% +/- 4.0%; p < 0.0001 compared with the control and ischemic-reperfused groups). Cyanide treatment produced rapid clearance, which was arrested by a return to the standard KH perfusate. Peak uptake as a percentage of injected dose was 74.9% +/- 1.4% for all groups combined. CONCLUSION: Thus 99mTcN-NOET has extremely high myocardial retention after 1 hour in normal myocardium and is not significantly affected by ongoing myocardial ischemia or reperfusion injury in this model. Clearance is increased markedly in extreme conditions of membrane disruption. These data are consistent with the concept that 99mTc-NOET is localized predominantly in or on cell membranes. 99mTcN-NOET is a promising, new myocardial perfusion imaging agent that exhibits a stable myocardial distribution in the setting of acute developing injury.

Effects of no flow and reperfusion on technetium-99m-Q12 kinetics.

UNLABELLED: The purpose of this study were to determine if 99mTc-Q12 tracer kinetics could be affected by the insult of total no flow followed by reflow and the effects of viability on clearance. METHODS: In six control buffer perfused rat hearts, flow was maintained at 12 ml/min throughout uptake and clearance. In six hearts (IR30), 30 min of no flow was followed by 60 min of reflow. In six hearts (IR60), 60 min of no flow was followed by 60 min of reflow. One millicurie 99mTc-Q12 was injected in control hearts or during reflow in the IR30 and IR60 hearts and myocardial clearance was monitored for 1 hr using a Nal detector. RESULTS: Control hearts demonstrated biphasic 99mTc-Q12 myocardial clearance with an early rapid clearance phase ending 5-10 min after injection (73.5% +/- 1.5% retention) followed by a late slow clearance phase (90.5% +/- 0.2% retention). IR30 hearts demonstrated a near identical clearance curve (74.3% +/- 0.9% early retention, 90.9% +/- 0.6% late retention). IR30 heart electron micrographs demonstrated predominantly ischemia insulted but viable cells. IR60 hearts also demonstrated a biphasic myocardial clearance, with a late slow phase similar to controls (91.9% +/- 0.6% retention). The early rapid phase was significantly faster than controls (61.1% +/- 3.4%). IR60 heart electron micrographs demonstrated predominantly injured nonviable cells. Well counting confirmed decreased retention in the IR60 rats compared to controls and IR30 rats. CONCLUSION: Technetium-99m-Q12 myocardial clearance is normally biphasic, with an early rapid phase ending after 5-10 min and a late slow phase. Ischemicaly insulted but viable myocardium created by 30 min of no flow followed by reflow has no effect on either clearance phase. This tracer warrants further study to determine its potential utility in assessing myocardial viability.

Technetium-99m sestamibi kinetics in reperfused canine myocardium.

The purpose of the current study was to clarify the myocardial kinetics of technetium-99m sestamibi when the latter is administered during reperfusion. Sestamibi has in the past been given to patients following thrombolytic therapy to document reperfusion and assess salvage. However, the factors which affect sestamibi kinetics during reperfusion are not clearly defined. In this study the left circumflex coronary artery was occluded for 2 h in six dogs (group 1) and for 3 h in six dogs (group 2), followed by reperfusion. Five additional dogs were not reperfused (group 3). Sestamibi was administered during reperfusion in groups 1 and 2, and during ongoing occlusion in group 3. Regional myocardial sestamibi activity was monitored for 3 h using miniature implanted radiation detectors and gamma camera imaging. Group 1 dogs had no infarcts, group 2 had moderate infarcts (mean: 13.9%), and group 3 had large infarcts (mean: 25.2%). Three-hour fractional myocardial clearances were significantly greater for reperfused infarcted (group 2) (0.23 +/- 0.02 SEM) and for nonreperfused infarcted myocardium (group 3) (0.24 +/- 0.02) compared to control (0.10 +/- 0.01) and reperfused noninfarcted myocardium (group 1) (0.07 +/- 0.02; P < 0.01). Quantitative image analysis demonstrated a significant reduction in the left circumflex/left anterior descending count ratios from initial to final scans for group 2 (0.74 +/- 0.03 to 0.65 +/- 0.03, P < 0.05), and a trend towards a reduction in the count ratios from initial to final scans for group 3 (0.38 +/- 0.04 to 0.30 +/- 0.04; P = 0.06).(ABSTRACT TRUNCATED AT 250 WORDS)