Quantitation of rat cerebral blood flow using 99mTc-HMPAO

INTRODUCTION

Technetium-99m-hexamethylpropyleneamine oxime (^99mTc-HMPAO) is potentially useful for the assessment of cerebral blood flow (CBF) in small animals. In this paper, a procedure for quantitation of rat CBF using ^99mTc-HMPAO was determined.

METHODS

Biodistribution of ^99mTc-radioactivity in normal rats was determined after intravenous administration of ^99mTc-HMPAO. Acetazolamide treated rats were intravenously administered with the mixture of ^99mTc-HMPAO and N-isopropyl-[¹²⁵I]iodoamphetamine ([¹²⁵I]IMP), and arterial blood was then collected for 5min. After blood sampling, the brain radioactivity concentration was measured with the auto-well γ counter.

RESULTS

The brain radioactivity concentration after intravenous administration of ^99mTc-HMPAO was steady from 14s to 60min post-injection. A double tracer experiment using ^99mTc-HMPAO and [¹²⁵I]IMP showed that 19s was the average of the optimal integration interval of arterial blood ^99mTc-radioactivity concentration to obtain CBF values measured by ^99mTc-HMPAO identical to those determined by [¹²⁵I]IMP. The CBF value determined by ^99mTc-HMPAO, calculated by dividing the brain radioactivity concentration at 5min post-injection by the integrated arterial blood radioactivity concentration until 19s post-injection, was well correlated with CBF as determined by [¹²⁵I]IMP.

CONCLUSION

These results suggest that the CBF quantitation procedure described in this paper could be useful for rat CBF assessment.

Effects of lactoferrin on the viability and the encystment of Acanthamoeba trophozoites

Lactoferrin (LF) is an iron-binding basic glycoprotein that has an antimicrobial effect against certain microbes. The purpose of this study is to evaluate the amoebicidal effect of bovine milk LF (bLF) against Acanthamoeba clinical-isolate trophozoites, which cause severe keratitis. Most of the risk factor for Acanthamoeba keratitis is from wearing soft contact lenses (SCLs). Acanthamoeba trophozoites were incubated in bovine LF (bLF) solution, and the ratios of viability and encystment were determined with microscopic analysis of cyst formation. The amoebicidal effect of bLF was assessed by Trypan blue assay. The ratios of viable cells in the presence of iron-free bLF (apo-bLF), native-bLF, and iron-saturated bLF (Fe-bLF) at the concentration of 10 μmol/L for 60 min were 7.7% ± 4.6%, 80.7% ± 10.1%, and 97.3% ± 1.5%, respectively. Apo-bLF showed potent amoebicidal effect against Acanthamoeba trophozoites, but Fe-bLF did not have this effect. After treating with apo-bLF, most dead cells were nonglobular forms of trophozoites but not cystic forms. Encystment of Acanthamoeba was assessed by the sarkosyl-calcofluor white assay. The encystment ratios treated with 0.5% propylene glycol (positive control) and 10 μmol/L apo-bLF for 24 h were 96.12% ± 10.6% and 0.47% ± 0.5%, respectively. These results suggest that the amoebicidal effect of apo-bLF without encystment might lead to the prevention of contamination of Acanthamoeba in SCL stock cases.

Development of a new tracer-encapsulated solid pellet injection system for more precise control of tracer-impurity-deposit location in LHD

A new tracer-encapsulated solid pellet (TESPEL) injection system has been developed additionally for the LHD heliotron. This system has three-dimensionally bended guide tubes, which allows us to inject the TESPEL obliquely on a poloidal cross-section of the LHD plasma. Consequently, this system enables us to control a tracer-impurity-deposited location more precisely. Moreover, this system can make it possible for the tracer impurity to be deposited even only inside the ergodic region (outside a last closed flux surface of the LHD plasma). A stereoscopic fast camera system has been also developed for capturing a three-dimensional TESPEL trajectory.

Development of a cascade arc discharge source for an atmosphere-vacuum interface device

To realize a novel vacuum-atmosphere interface that does not require a large differential pumping system, a robust cascade arc discharge source called a plasma window is constructed and tested for long-term operation. By modifying a test plasma with a direct current discharge, a vacuum interface with a high gas pressure ratio of 1/407 between the discharge and expansion sections is demonstrated for currents as high as 20 A. No significant damage to the electrodes is observed during the operation. Analysis of the visible emission spectra reveals that a stationary, stable argon plasma having a temperature of 1 eV and a density of 1.5 × 10(16) cm(-3) is generated in the plasma channel.

Lactobacillus rhamnosus GG increases Toll-like receptor 3 gene expression in murine small intestine ex vivo and in vivo

Administration of Lactobacillus rhamnosus GG (LGG) has been reported to be therapeutically effective against acute secretory diarrhoea resulting from the structural and functional intestinal mucosal lesions induced by rotavirus infection; however, the underlying mechanisms remain to be completely elucidated. Because Toll-like receptor 3 (TLR3) plays a key role in the innate immune responses following the recognition of rotavirus, the present study examined whether LGG influences TLR3 gene expression in murine small intestine ex vivo and in vivo. We employed cultured intestinal organoids derived from small intestinal crypts as an ex vivo tissue model. LGG supplementation increased TLR3 mRNA levels in the intestinal organoids, as estimated by quantitative real-time polymerase chain reaction. Likewise, single and 7-day consecutive daily administrations of LGG increased TLR3 mRNA levels in the small intestine of C57BL/6N mice. The mRNA levels of other TLRs were not substantially altered both ex vivo and in vivo. In addition, LGG supplementation increased the mRNA levels of an antiviral type 1 interferon, interferon-α (IFN-α), and a neutrophil chemokine, CXCL1, upon stimulation with a synthetic TLR3 ligand, poly(I:C) in the intestinal organoids. LGG administration did not alter IFN-α and CXCL1 mRNA levels in the small intestine in vivo. Supplementation of other bacterial strains, Bifidobacterium bifidum and Lactobacillus paracasei, failed to increase TLR3 and poly(I:C)-stimulated CXCL1 mRNA levels ex vivo. We propose that upregulation of TLR3 gene expression may play a pivotal role in the therapeutic efficacy of LGG against rotavirus-associated diarrhoea. In addition, we demonstrated that intestinal organoids may be a promising ex vivo tissue model for investigating host-pathogen interactions and the antiviral action of probiotics in the intestinal epithelium.

Lipid-rich bovine serum albumin improves the viability and hatching ability of porcine blastocysts produced in vitro

The effects of lipid-rich bovine serum albumin (LR-BSA) on the development of porcine blastocysts produced in vitro were examined. Addition of 0.5 to 5 mg/ml LR-BSA to porcine blastocyst medium (PBM) from Day 5 (Day 0 = in vitro fertilization) significantly increased the hatching rates of blastocysts on Day 7 and the total cell numbers in Day-7 blastocysts. When Day-5 blastocysts were cultured with PBM alone, PBM containing LR-BSA, recombinant human serum albumin or fatty acid-free BSA, addition of LR-BSA significantly enhanced hatching rates and the cell number in blastocysts that survived compared with other treatments. The diameter, ATP content and numbers of both inner cell mass and total cells in Day-6 and Day-7 blastocysts cultured with PBM containing LR-BSA were significantly higher than in blastocysts cultured with PBM alone, whereas LR-BSA had no effect on mitochondrial membrane potential. The mRNA levels of enzymes involved in fatty acid metabolism and β-oxidation (ACSL1, ACSL3, CPT1, CPT2 and KAT) in Day-7 blastocysts were significantly upregulated by the addition of LR-BSA. The results indicated that LR-BSA enhanced hatching ability and quality of porcine blastocysts produced in vitro, as determined by ATP content, blastocyst diameter and expression levels of the specific genes, suggesting that the stimulatory effects of LR-BSA arise from lipids bound to albumin.

Analysis of a rice fickle spikelet1 mutant that displays an increase in flower and spikelet organ number with inconstant expressivity

In rice (Oryza sativa), floral organs develop in the spikelet, an inflorescence unit unique to grass species. The floral organs, such as carpels, stamens and lodicules, are enclosed by two spikelet organs, the palea and lemma. The number of floral organs is genetically regulated. Mutations in the FLORAL ORGAN NUMBER (FON) genes cause an increase in the number of carpels and stamens due to an enlargement of the floral meristem. The spikelet organs, such as lemma and palea, are less affected in the fon mutants. We found a mutant, fickle spikelet1 (fsp1), that displayed an increased number not only of floral organs but also of spikelet organs. Because the fsp1 spikelets showed a pleiotropic phenotype, we classified them into four types. The expressivity of the fsp1 phenotype varied from plant to plant, and also from panicle to panicle within a single plant. In addition, the frequency of each fsp1 spikelet type also varied considerably among plants and among panicles within a plant. When the fsp1 mutants were grown in a growth chamber, an extra abnormality, namely a defect in pollen development, was observed. Furthermore, the expressivity of the mutant phenotype increased dramatically in mutant plants grown in a growth chamber. Thus, the expressivity of the fsp1 phenotype seems to be strongly influenced by environmental conditions.

Preclinical assessment of early tumor response after irradiation by positron emission tomography with 2-amino-[3-¹¹C]isobutyric acid

The positron emission tomography (PET) probe, 2-amino-[3-¹¹C]isobutyric acid ([3-¹¹C]AIB), is reported to accumulate less in inflammatory lesions than 2-deoxy-2-[¹⁸F]fluoro-D-glucose ([¹⁸F]FDG) and has the potential for evaluation of the efficacy of radiotherapy. To determine whether [3-¹¹C]AIB is useful to monitor early metabolic change in tumors after radiotherapy, we evaluated the temporal change in [3-¹¹C]AIB tumor uptake, tumor volume, histological features and expression of amino acid transporters early after radiotherapy in a mouse tumor model. PET with [3-¹¹C]AIB was conducted in mice bearing a subcutaneous tumor (SY, derived from small cell lung cancer) in two schedules: schedule 1, before (day -1) and after (days 1 and 3) 15 Gy of radiation and schedule 2, days -1, 1 and 5. [3-¹¹C]AIB tumor uptake tended to increase on day 1 after irradiation and decreased thereafter. Tumor uptake was not correlated with tumor volume in schedule 1. Although tumor uptake was correlated with tumor volume in schedule 2, this correlation was lost when the day 5 data of greatly reduced tumor volumes were excluded. In a separate group of tumor-bearing mice, excised tumor sections were stained with terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling (TUNEL) or anti-Ki-67 antibody. There was no correlation between tumor uptake and percentages of TUNEL- or Ki-67-positive cells. Expression of amino acid transporters, SLC38A1, SLC38A2 and SLC38A4, was determined by real-time RT-PCR. SLC38A1 and SLC38A2 were expressed in SY tumors, and a significant correlation was observed between [3-¹¹C]AIB tumor uptake and SLC38A1 expression. In conclusion, early change in [3-¹¹C]AIB tumor uptake after irradiation reflected the temporal change in amino acid transporter expression, while it was independent of change in tumor volume, apoptosis and cell proliferation. PET with [3-¹¹C]AIB has the potential for use in non-invasive evaluation of early metabolic change after irradiation before morphological change of tumors.

Inhibition of radical reactions for an improved potassium tert-butoxide-promoted (11) C-methylation strategy for the synthesis of α-(11) C-methyl amino acids

α-(11) C-Methyl amino acids are useful tools for biological imaging studies. However, a robust procedure for the labeling of amino acids has not yet been established. In this study, the (11) C-methylation of Schiff-base-activated α-amino acid derivatives has been optimized for the radiosynthesis of various α-(11) C-methyl amino acids. The benzophenone imine analog of methyl 2-amino butyrate was (11) C-methylated with [(11) C]methyl iodide following its initial deprotonation with potassium tert-butoxide (KOtBu). The use of an alternative base such as tetrabutylammonium fluoride, triethylamine, and 1,8-diazabicyclo[5.4.0]undec-7-ene did not result in the (11) C-methylated product. Furthermore, the KOtBu-promoted (11) C-methylation of the Schiff-base-activated amino acid analog was enhanced by the addition of 1,2,4,5-tetramethoxybenzene or 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) and inhibited by the addition of 1,10-phenanthroline. These results suggest that inhibition of radical generation induced by KOtBu improves the α-(11) C-methylation of the Schiff-base-activated amino acids. The addition of a mixture of KOtBu and TEMPO to a solution of Schiff-base-activated amino acid ester and [(11) C]methyl iodide provided optimal results, and the tert-butyl ester and benzophenone imine groups could be readily hydrolyzed to give the desired α-(11) C-methyl amino acids with a high radiochemical conversion. This strategy could be readily applied to the synthesis of other α-(11) C-methyl amino acids.

Preclinical characterization of 5-amino-4-oxo-[6-11C]hexanoic acid as an imaging probe to estimate protoporphyrin IX accumulation induced by exogenous aminolevulinic acid

Preoperative noninvasive imaging to estimate the quantity and spatial distribution of protoporphyrin IX (PpIX) accumulation in tumors induced by 5-aminolevulinic acid (ALA) administration is expected to improve the efficacy of ALA-based fluorescence-guided resection and photo- and sonodynamic therapies. PpIX synthesis from exogenous ALA has been reported to be regulated by ALA influx or ALA dehydratase (ALAD) activity, which catalyzes the first step of the synthesis. In this study, we characterized the properties of a (11)C-labeled ALA analog, 5-amino-4-oxo-[6-(11)C]hexanoic acid ((11)C-MALA), as a PET tracer to estimate PpIX accumulation.

METHODS

In vitro uptake of (11)C-MALA and (3)H-ALA was determined in 5 tumor cell lines after 10-min incubation with each tracer at 37°C. The expression levels of ALAD were determined by Western blot analysis. In vivo distribution and dynamic PET studies were conducted in tumor-bearing mice. In vitro and in vivo accumulation of ALA-induced PpIX was determined by measuring fluorescence in extracts of cells or tumors.

RESULTS

In vitro uptake of (11)C-MALA in 5 tumor cell lines was correlated with ALAD expression levels and PpIX accumulation. In vivo biodistribution and dynamic PET studies showed that (11)C-MALA was rapidly incorporated into tumors, and the tumor-to-muscle ratio of (11)C-MALA at 1 min after injection was significantly correlated with that of (3)H-ALA. (11)C-MALA in tumors was continuously decreased thereafter, and the elimination rate of (11)C-MALA from AsPC-1 tumors with the highest ALAD expression level was slower than from other tumors with lower expression levels. These results suggest that the influx and intracellular retention of (11)C-MALA reflect ALA influx and ALAD expression levels, respectively. Tumor accumulation of (11)C-MALA at 60 min after injection was strongly correlated with PpIX accumulation in tumor tissues.

CONCLUSION

(11)C-MALA PET has the potential to noninvasively estimate the quantitative and spatial accumulation of exogenous ALA-induced PpIX.

Altered superoxide dismutase activity by carbohydrate utilization in a Lactococcus lactis strain

Reactive oxygen species, such as superoxide, can damage cellular components, such as proteins, lipids, and DNA. Superoxide dismutase (SOD) enzymes catalyze the conversion of superoxide anions to hydrogen peroxide and dioxygen. SOD is present in most lactococcal bacteria, which are commonly used as starters for manufacturing fermented dairy products and may have health benefits when taken orally. We assessed the effects of carbohydrate use on SOD activity in lactococci. In Lactococcus lactis ssp. lactis G50, the SOD activity of cells grown on lactose and galactose was higher than that on glucose; in Lactococcus lactis ssp. cremoris H61, SOD activity was independent of the type of carbohydrate used. We also investigated the activity of NADH oxidase, which is related to the production of superoxide in strains G50 and H61. Activity was highest in G50 cells grown on lactose, lower on galactose, and lowest on glucose, whereas activity in H61 cells did not differ with the carbohydrate source used. The SOD and NADH oxidase activities of strain G50 in three carbohydrates were linked. Strain G50 fermented lactose and galactose to lactate, acetate, formate, and ethanol (mixed-acid fermentation) and fermented glucose to mainly lactate (homolactic fermentation). Strain H61 fermented glucose, lactose, and galactose to mainly lactate (homolactic fermentation). In strain G50, when growth efficiency was reduced by adding a metabolic inhibitor to the growth medium, SOD activity was higher than in the control; however, the metabolism was homofermentative. Aerobic conditions, but not glucose-limited conditions, increased SOD activity, and mixed-acid fermentation occurred. We conclude that the effect of carbohydrate on SOD activity in lactococci is strain dependent and that the activity of commercial lactococci can be enhanced through carbohydrate selection for mixed-acid fermentation or by changing the energy distribution, thus enhancing the value of the starter and the resulting dairy products.