System ASC Research Articles

The differences in postprandial free amino acid concentrations and the gene expression of PepT1 and amino acid transporters after fishmeal partial replacement by meat and bone meal in juvenile turbot (Scophthalmus maximus L.)

Meat and bone meal (MBM) is a high-quality alternative protein source used to replace fishmeal (FM). However, the molecular mechanisms of over-substituted FM by MBM resulted in growth reduction are still not clear. The objective of the study was to evaluate the effect of FM replacement by MBM on the concentration of postprandial free amino acid (FAA) and mRNA abundance of peptide and amino acid transporters in juvenile turbot (Scophthalmus maximus L.). Fish were fed with FM diet (60% FM), MBM diet (33% FM + 34.2% MBM) and MBM + AA diet (MBM diet with essential amino acid (EAA) added to match the AA profile of FM) for 30 days. Results showed that compared with the FM diet, MBM diet led to a reduction in FAA concentration peak values in plasma and muscle. MBM + AA diet significantly elevated the peak values of FAA concentrations to FM diet level in plasma, but not in muscle. Furthermore, compared with FM diet, MBM diet significantly increased gene expression of PepT1 and major amino acid transporters in intestine, whereas MBM diet greatly downregulated gene expression of T-type amino acid transporter-1, system ASC amino acid transporter-2 and cationic amino acid transporter-2 in muscle. Supplemented EAA did not ameliorate these different effects in intestine and muscle. Overall, this study provided a comprehensive explanation for the relationship between diet, FAA concentrations and AA transportations, which provides a molecular basis for further using MBM to replace FM in aquafeeds.

At Least Three Transporters Likely Mediate Threonine Uptake Needed for Mouse Embryonic Stem Cell Proliferation.

Stem cells are at the forefront of current regenerative and biomedical research. Thus, there exists an imperative and urgent need to understand the mechanisms that drive stem cell function in order to exploit their use as a therapeutic tool. Amino acids are potent inducers of signaling cascades that drive stem cell proliferation and differentiation. With a focus on mouse embryonic stem (mES) cells, Threonine (Thr) is the only amino acid required in culture media for mES cell proliferation. Current research associates this need for Thr with threonine dehydrogenase (TDH), which catabolizes Thr to glycine and acetyl-CoA in mES cells. This theory depends, in part, on the ability of 3- hydroxynorvaline (3-HNV) to inhibit both TDH and mES cell proliferation. However, the concentration of 3-HNV needed to inhibit mES cell proliferation is more than an order of magnitude less than its apparent Ki for TDH inhibition. Additionally, 3-HNV inhibits human embryonic stem (hES) cell proliferation, but hES cells do not express a functional tdh gene. Such findings indicate another mechanism for Thr stimulated mES and hES cell proliferation. Since amino acid transporters may be inducers of signaling cascades, we characterized the Thr transport systems in mES cells. We found that there is a Na+-dependent and a Na+-independent component of substrate-saturable transport, with the Na+-dependent component predominating. We also found that of 20 amino acids tested, the amino acids that were the strongest inhibitors of the Na+-dependent component of radiolabeled Thr transport were Ser, Cys, 4-OH-Pro, Asn, Met, and non-radiolabeled Thr itself. Such findings are consistent with characteristics of the ASC transport system, suggesting that this ASC system is responsible for the majority of Thr transport in mES cells. We confirmed expression of mRNA encoding the ASC system transporters, ASCT1 and ASCT2, in mES cells using RT-PCR. In conclusion, mES cells likely express at least three transporters of Thr; at least two Na+-dependent transporters and one Na+-independent one.

14C]Fluciclovine (alias anti-[14C]FACBC) uptake and ASCT2 expression in castration-resistant prostate cancer cells

Introductiontrans-1-Amino-3-[18F]fluorocyclobutanecarboxylic acid ([18F]fluciclovine, also known as anti-[18F]FACBC), is a tracer for positron emission tomography (PET) imaging for detection of tumors such as prostate cancer (PCa). Our previous study showed that ASCT2 (Na+-dependent amino acid transporter (AAT)) mediates fluciclovine uptake in androgen-dependent PCa cells; its expression is influenced by androgen, a key hormone in the progression of primary PCa and castration-resistant prostate cancer (CRPC). In this study, we investigated the uptake mechanisms and feasibility of [18F]fluciclovine for CRPC in the androgen-dependent PCa cell line LNCaP and LNCaP-derivatives LNCaP-SF and LN-REC4. MethodsLNCaP-SF was established after long-term cultivation of LNCaP in steroid-free conditions, and LN-Pre and LN-REC4 were established from LNCaP inoculated in intact and castrated severe combined immunodeficient mice, respectively. Uptake and competitive inhibition experiments were performed with trans-1-amino-3-fluoro[1-14C]cyclobutanecarboxylic acid ([14C]fluciclovine) to characterize the involvement of AATs in androgen-dependent PCa (LNCaP and LN-Pre) and CRPC-like (LNCaP-SF and LN-REC4) cell lines. AAT expression was analyzed by Western blotting, and [14C]fluciclovine uptake in androgen-dependent PCa and CRPC-like cell lines were investigated in the presence or absence of dihydrotestosterone (DHT). ResultsThe contribution of Na+-dependent AATs to [14C]fluciclovine uptake in all cell lines was 88−98%, and [14C]fluciclovine uptake was strongly inhibited by l-glutamine and l-serine, the substrates for Na+-dependent alanine-serine-cysteine (system ASC) AATs, in the presence of Na+. DHT enhanced ASCT2 expression in LNCaP, LN-Pre, and LN-REC4, but not in LNCaP-SF, and the responses of ASCT2 expression to DHT correlated with [14C]fluciclovine uptake. ConclusionsSystem ASC, especially ASCT2, could play a major role in [14C]fluciclovine uptake into CRPC-like and androgen-dependent PCa cells, suggesting [18F]fluciclovine-PET is applicable to the detection of CRPC as well as androgen-dependent PCa. Advance in knowledge[18F]fluciclovine-PET may be applied for the detection of CRPC. Implication for patient care[18F]fluciclovine-PET may permit early intervention for CRPC treatment.

Expression of Amino Acid Transporters (LAT1 and ASCT2) in Patients with Stage III/IV Laryngeal Squamous Cell Carcinoma.

The aim of this study is to evaluate the clinicopathological significance of L-type amino acid transporter 1 (LAT1) expression in patients with advanced laryngeal squamous cell carcinoma (LSCC). A total of 73 patients with advanced LSCC were retrospectively reviewed. Tumor sections were stained by immunohistochemistry for LAT1, 4F2hc, system ASC amino acid transporter-2 (ASCT2), cell proliferation by Ki-67, microvessel density (MVD) determined by CD34 and p53. A positive LAT1, 4F2hc and ASCT2 expression (staining more than a quarter) in the primary sites were recognized in 85, 80 and 45 %, respectively, and a high LAT1, 4F2hc and ASCT2 expression (staining more than a half) yielded 48, 31 and 18 %, respectively. High expression of LAT1 was significantly associated with lymph node metastasis, 4F2hc, ASCT2, Ki-67 and p53. The expression of LAT1 was significantly correlated with ASCT2, 4F2hc, cell proliferation, and MVD. By univariate analysis, there was no statistically significant relationship between LAT1 expression and prognosis in advanced LSCC. LAT1, 4F2hc and ASCT2 were highly expressed in patients with advanced laryngeal cancer. Our study suggests that the expression of LAT1 plays a crucial role in the metastasis and tumor progression in advanced LSCC.

Characterization of L‐Threonine transport in mouse embryonic stem cells

Stem cells are at the forefront of current regenerative and biomedical research. There exists an imperative need to understand the mechanisms that drive stem cell function in order to exploit their use as a therapeutic tool. Amino acids are potent inducers of signaling cascades that drive stem cell proliferation and differentiation. With a focus on mouse embryonic stem (mES) cells, L‐threonine is the only amino acid required in culture medium for mES cell proliferation. Current research associates this need for L‐threonine with threonine dehydrogenase (TDH), which catabolizes L‐threonine to glycine and acetyl‐CoA in mES cells. While this may be true for mES cells, human embryonic stem (hES) cells do not express a functional tdh gene. Additionally, the concentration of 3‐hydroxynorvaline (3‐HNV), a potent inhibitor of TDH, needed to inhibit mES cell proliferation is more than an order of magnitude less than the apparent Ki for TDH inhibition. Such findings suggest a different mechanism responsible for the relationship between L‐threonine and ES cell proliferation, which may be explained by Thr transport. To explore this novel idea, we characterized the L‐threonine transport systems in mES cells by conducting radiolabelling transport studies. We found that there is a Na+‐dependent and Na+‐independent component of transport, with the Na+‐dependent component predominating. We also found that Thr, Ser, Cys, Ala, 4‐OH‐Pro, Asn, 3‐HNV, and Met were the strongest inhibitors of the Na+‐dependent component of transport. Such findings are consistent with characteristics of the ASC transport system, suggesting that this system is responsible for majority of Thr transport in mES cells. We confirmed the presence of the ASC system transporters, ASCT1 and ASCT2, in mES cells using RT‐PCR. Project supported by Midwestern University.

Synthesis and preliminary biological evaluation of S-11C-methyl-D-cysteine as a new amino acid PET tracer for cancer imaging.

S-(11)C-methyl-L-cysteine (LMCYS) is an attractive amino acid tracer for clinical tumor positron emission tomography (PET) imaging. D-isomers of some radiolabeled amino acids are potential PET tracers for tumor imaging. In this work, S-(11)C-methyl-D-cysteine (DMCYS), a D-amino acid isomer of S-(11)C-methyl-cysteine for tumor imaging was developed and evaluated. DMCYS was prepared by (11)C-methylation of the precursor D-cysteine, with an uncorrected radiochemical yield over 50% from (11)CH3I within a total synthesis time from (11)CO2 about 12min. In vitro competitive inhibition studies showed that DMCYS uptake was primarily transported through the Na(+)-independent system L, and also the Na(+)-dependent system B(0,+) and system ASC, with almost no system A. In vitro incorporation experiments indicated that almost no protein incorporation was found in Hepa 1-6 hepatoma cell lines. Biodistribution studies demonstrated higher uptake of DMCYS in pancreas and liver at 5min post-injection, relatively lower uptake in brain and muscle, and faster radioactivity clearance from most tissues than those of L-isomer during the entire observation time. In the PET imaging of S180 fibrosarcoma-bearing mice and turpentine-induced inflammatory model mice, 2-(18)F-fluoro-2-deoxy-D-glucose (FDG) exhibited significantly high accumulation in both tumor and inflammatory lesion with low tumor-to-inflammation ratio of 1.40, and LMCYS showed low tumor-to-inflammation ratio of 1.64 at 60min post-injection. By contrast, DMCYS showed moderate accumulation in tumor and very low uptake in inflammatory lesion, leading to relatively higher tumor-to-inflammation ratio of 2.25 than (11)C-methyl-L-methionine (MET) (1.85) at 60min post-injection. Also, PET images of orthotopic transplanted glioma models demonstrated that low uptake of DMCYS in normal brain tissue and high uptake in brain glioma tissue were observed. The results suggest that DMCYS is a little better than the corresponding L-isomers as a potential PET tumor-detecting agent and is superior to MET and FDG in the differentiation of tumor from inflammation.

Expression of amino acid transporters (LAT1, ASCT2 and xCT) as clinical significance in hepatocellular carcinoma.

Amino acid transporters play an important role in tumor progression and survival of cancer cells. However, the prognostic significance of L-type amino acid transporter 1 (LAT1), system ASC amino acid transporter-2 (ASCT2) and xCT expression in patients with hepatocellular carcinoma (HCC) remains unclear. The aim of this study is to investigate the clinicopathological significance of these amino acid transporters in patients with HCC. We examined 84 patients with surgically resected HCC. Tumor sections were stained by immunohistochemistry for LAT1, ASCT2, xCT, 4F2hc/CD98hc (4F2hc), Ki-67 and microvessel density (MVD) determined by CD34. LAT1, 4F2hc, ASCT2 and xCT were positively expressed in 61% (50/84), 77% (65/84), 63% (53/84) and 65% (55/84), respectively. Positive LAT1 expression was significantly associated with 4F2hc expression, Ki-67 and the serum albumin. By univariate analysis, LAT1 expression, disease stage and albumin had a significant relationship with overall survival. Tumor size, disease stage, portal vein invasion, albumin and α-fetoprotein had a significant relationship with progression-free survival. Multivariate analysis confirmed that LAT1 expression is an independent and significant prognostic factor for predicting worse outcome after surgery. LAT1 can serve as a significant prognostic marker for predicting negative prognosis after surgery.

Synthesis and evaluation of 2-amino-5-(4-[(18)F]fluorophenyl)pent-4-ynoic acid ([(18)F]FPhPA): a novel (18)F-labeled amino acid for oncologic PET imaging.

(18)F-labeled amino acids are important PET radiotracers for molecular imaging of cancer. This study describes synthesis and radiopharmacological evaluation of 2-amino-5-(4-[(18)F]fluorophenyl)pent-4-ynoic acid ([(18)F]FPhPA) as a novel amino acid radiotracer for oncologic imaging. (18)F]FPhPA was prepared using Pd-mediated Sonogashira cross-coupling reaction between 4-[(18)F]fluoroiodobenzene ([(18)F]FIB) and propargylglycine. The radiopharmacological profile of [(18)F]FPhPA was evaluated in comparison with O-(2-[(18)F]fluoroethyl)-L-tyrosine ([(18)F]FET) using the murine breast cancer cell line EMT6 involving cellular uptake studies, radiotracer uptake competitive inhibition experiments and small animal PET imaging. (18)F]FPhPA was prepared in 42±10% decay-corrected radiochemical yield with high radiochemical purity >95% after semi-preparative HPLC purification. Cellular uptake of L-[(18)F]FPhPA reached a maximum of 58±14 % radioactivity/mg protein at 90 min. Lower uptake was observed for racemic and D-[(18)F]FPhPA. Radiotracer uptake inhibition studies by synthetic and naturally occurring amino acids suggested that Na(+)-dependent system ASC, especially ASCT2, and Na(+)-independent system L are important amino acid transporters for [(18)F]FPhPA uptake into EMT6 cells. Small animal PET studies demonstrated similar high tumor uptake of [(18)F]FPhPA in EMT6 tumor-bearing mice compared to [(18)F]FET reaching a maximum standardized uptake value (SUV) of 1.35 after 60 min p.i.. Muscle uptake of [(18)F]FPhPA was higher (SUV30min=0.65) compared to [(18)F]FET (SUV30min=0.40), whereas [(18)F]FPhPA showed a more rapid uptake and clearance from the brain compared to [(18)F]FET. L-[(18)F]FPhPA is the first (18)F-labeled amino acid prepared through Pd-mediated cross-coupling reaction. L-[(18)F]FPhPA displayed promising properties as a novel amino acid radiotracer for molecular imaging of system ASC and system L amino acid transporters in cancer.

Prognostic significance of amino-acid transporter expression (LAT1, ASCT2, and xCT) in surgically resected tongue cancer.

Background:Amino-acid transporters are necessary for the tumour cell growth and survival, and have a crucial role in the development and invasiveness of cancer cells. But, it remains unclear about the prognostic significance of L-type amino-acid transporter 1 (LAT1), system ASC amino-acid transporter-2 (ASCT2), and xCT expression in patients with tongue cancer. We conducted the clinicopathological study to investigate the protein expression of these amino-acid transporters in tongue cancer.Methods:Eighty-five patients with surgically resected tongue cancer were evaluated. Tumour sections were stained by immunohistochemistry for LAT1, ASCT2, xCT, 4F2hc/CD98hc (4F2hc), Ki-67, and microvessel density (MVD) determined by CD34, and p53.Results:L-type amino-acid transporter 1 and 4F2hc were highly expressed in 61% (52 out of 85) and 45% (38 out of 47), respectively. ASC amino-acid transporter-2 and xCT were positively expressed in 59% (50 out of 85) and 21% (18 out of 85), respectively. The expression of both LAT1 and ASCT2 was significantly associated with disease staging, lymph-node metastasis, lymphatic permeation, 4F2hc expression and cell proliferation (Ki-67). xCT expression indicated a significant association with advanced stage and tumour factor. By univariate analysis, disease staging, lymphatic permeation, vascular invasion, LAT1, ASCT2, 4F2hc, and Ki-67 had a significant relationship with overall survival. Multivariate analysis confirmed that LAT1 was an independent prognostic factor for predicting poor prognosis.Conclusions:L-type amino-acid transporter 1 and ASCT2 can serve as a significant prognostic factor for predicting worse outcome after surgical treatment and may have an important role in the development and aggressiveness of tongue cancer.

Agility appraisement framework for integrated supply chain using generalised interval-valued fuzzy set

In today's competitive industries, several issues arise on organisational agile supply chain ASC such as organisational resistance to change, inter-functional conflicts, joint production planning, team oriented performance measures, shifts in channel power, information sharing, real time communication, and technical compatibility. Such issues are relevant to both manufacturing as well as service sectors. The objective of this reporting is to contribute important insights to the extant body of knowledge in ASC. Complexity, ambiguity and vagueness involved in agility evaluation process must be overcome for agility estimation related an ASC system. Interval-valued fuzzy numbers IVFNs set theory has been efficiently explored in order to assess the extent of contributions imposed by complicated agility capabilities in an ambiguous fuzzy environment. Application of the said approach as a decision support system DSS evidently helps the management practitioners to conduct gap analysis between existent agility level and the desired one; and also provides reliable information for decision making. The proposed procedure has efficiently been applied to a large scale automobile manufacturing company in India, as a case study.

Differences in Transport Mechanisms of trans-1-Amino-3-[18F]Fluorocyclobutanecarboxylic Acid in Inflammation, Prostate Cancer, and Glioma Cells: Comparison with l-[Methyl-11C]Methionine and 2-Deoxy-2-[18F]Fluoro-d-Glucose

We aimed to elucidate trans-1-amino-3-[(18)F]fluorocyclobutanecarboxylic acid (anti-[(18)F]FACBC) uptake mechanisms in inflammatory and tumor cells, in comparison with those of L-[methyl-(11)C]methionine ([(11)C]Met) and 2-deoxy-2-[(18)F]fluoro-D-glucose ([(18)F]FDG). Using carbon-14-labeled tracers, in vitro time-course, pH dependence, and competitive inhibition uptake experiments were performed in rat inflammatory (T cells, B cells, granulocytes, macrophages), prostate cancer (MLLB2), and glioma (C6) cells. Anti-[(14)C]FACBC uptake ratios of T/B cells to tumor cells were comparable, while those of granulocytes/macrophages to tumor cells were lower than those for [(14)C]FDG. Over half of anti-[(14)C]FACBC uptake by T/B and tumor cells was mediated by Na(+)-dependent amino acid transporters (system ASC), whereas most [(14)C]Met transport in all cells was mediated by Na(+)-independent carriers (system L). The low anti-[(18)F]FACBC accumulation in granulocytes/macrophages may be advantageous in discriminating inflamed regions from tumors. The significant anti-[(18)F]FACBC uptake in T/B cells may cause false-positives in some cancer patients who undergo FACBC-positron emission tomography (PET).

Comparative evaluation of transport mechanisms of trans-1-amino-3-[18F]fluorocyclobutanecarboxylic acid and l-[methyl-11C]methionine in human glioma cell lines

Positron emission tomography (PET) with amino acid tracers is useful for the visualization and assessment of therapeutic effects on gliomas. Our purpose is to elucidate the transport mechanisms of trans-1-amino-3-[18F]fluorocyclobutanecarboxylic acid (anti-[18F]FACBC) and l-[methyl-11C]methionine ([11C]Met) in normal human astrocytes (NHA), low-grade (Hs683, SW1088), and high-grade (U87MG, T98G) human glioma cell lines. Because the short half-lives of fluorine-18 and carbon-11 are inconvenient for in vitro experiments, trans-1-amino-3-fluoro[1-14C]cyclobutanecarboxylic acid (anti-[14C]FACBC) and l-[methyl-14C]methionine ([14C]Met) were used instead of the PET tracers. Time-course uptake experiments showed that uptake of anti-[14C]FACBC was 1.4–2.6 times higher than that of [14C]Met in NHA and low-grade glioma cells, and was almost equal to that of [14C]Met in high-grade glioma cells. To identify the amino acid transporters (AATs) involved in the transport of anti-[14C]FACBC and [14C]Met, we carried out competitive inhibition experiments using synthetic/naturally-occurring amino acids as inhibitors. We found that anti-[14C]FACBC uptake in the presence of Na+ was strongly inhibited by l-glutamine and l-serine (the substrates for ASC system AATs), whereas l-phenylalanine and 2-amino-bicyclo[2,2,1]heptane-2-carboxylic acid (BCH, the substrates for L system AATs) robustly inhibited Na+-independent anti-[14C]FACBC uptake. Regardless of Na+, [14C]Met uptake was inhibited strongly by l-phenylalanine and BCH. Moreover, the exchange transport activity of l-glutamine for anti-[14C]FACBC was stronger than that of BCH in the presence of Na+, whereas that for [14C]Met was almost equal to BCH. These results demonstrate that ASC and L are important transport systems for anti-[18F]FACBC uptake, while system L is predominantly involved in [11C]Met transport in human astrocytes and glioma cells.

Synthesis and biological evaluation of N-(2-[18F]Fluoropropionyl)-L-methionine for tumor imaging

N-position radiolabeled amino acids, such as N-(2-[(18)F]fluoropropionyl)-L-methionine ([(18)F]FPMET) as a derivative of L-methionine (MET), can potentially serve as a PET tracer for tumor imaging. In the current study, radiosynthesis and biological evaluation of [(18)F]FPMET as a new PET tumor agent are performed. [(18)F]FPMET was synthesized by reacting 4-nitrophenyl 2-[(18)F]fluoropropionate ([(18)F]NFP) with MET. In vitro competitive inhibition and protein incorporation experiments were performed with Hepa1-6 hepatoma cell lines. The biodistribution of [(18)F]FPMET was determined in S180 fibrosarcoma-bearing mice. PET/CT studies of [(18)F]FPMET were conducted in S180 fibrosarcoma-bearing mice, A549 lung adenocarcinoma-bearing nude mice, and PC-3 prostate cancer-bearing nude mice. [(18)F]FPMET was synthesized in 72%± 4% uncorrected radiochemical yield (n=10) from [(18)F]NFP. In vitro experiments showed that [(18)F]FPMET was primarily transported through Na(+)-dependent system A, system ASC, and system B(0,+), and was not incorporated into protein. Biodistribution and PET/CT imaging studies indicated that [(18)F]FPMET could delineate S180 fibrosarcoma, A549 lung adenocarcinoma, and PC-3 prostate cancer. An efficient synthesis of N-position [(18)F]labeled amino acids with a classic [(18)F]NFP prosthetic group is developed. The results support that [(18)F]FPMET seems to be a potential tracer for tumor imaging with PET.

Experimental and modeling study of a dual-layer (SCR + PGM) NH3 slip monolith catalyst (ASC) for automotive SCR after treatment systems. Part 2. Validation of PGM kinetics and modeling of the dual-layer ASC monolith

We present herein the final part in the development and validation of a chemically and physically consistent mathematical model of a commercial dual-layer (SCR+PGM) monolithic NH3 slip converter (ASC). Specifically, in this conclusive Part 2 of the project we first validate the global kinetic model for the PGM catalyst component, previously developed in Part 1 over the precursor powders, against data collected over a single-layer coated monolith. Then, we incorporate validated kinetics for the two individual SCR and PGM components into a dual-layer ASC monolith catalyst model and proceed to a systematic validation against experimental catalytic activity data collected over core samples of the dual-layer ASC system. A DOE approach is also adopted in order to secure a uniform coverage of the operating field.A positive interaction of the PGM and SCR catalytic chemistries is emphasized by the data collected over the dual-layer SCR+PGM monolith catalyst, leading to largely enhanced N2 selectivities as compared to a single-layer PGM-only washcoat. We show that such a beneficial interaction between the PGM and SCR chemistries occurs via diffusion/reaction of NH3 and NOx in the SCR catalyst layer. Results prove that the dual-layer ASC model can simulate realistically the actual NH3 slip catalyst configuration over a wide range of representative conditions.

The economics of automatic section control technology for planters: A case study of middle and west Tennessee farms

Reducing double-planted area in row crop production fields where planter overlap is unavoidable, such as end rows, point rows, and areas around internal field obstacles, can improve net returns by reducing seed costs and increasing revenue. The objective of this case study was to present a summary of results from 52 fields that highlight potential losses from double-planted areas and therefore potential savings associated with an investment in an Automatic Section Control system (ASC) for planters. Percentage of double-planted area ranged from 0.1% to 15.5% depending on field size and shape. Fields were classified into low, moderate and high double-planted fields, based on percentage of double planted area. Potential savings from adopting ASC system for planters were evaluated using this information. Savings from the adoption of this technology ranged from $4 per ha to $26 per ha depending on the distribution of field types in a farming operation. The results indicated that savings and the minimum period of time over which an investment in ASC on planters would have to be finance to guarantee a positive net cash flow every year was determined by farm size and distribution of field types in a farming operation.

Automated Timetabling Using Stochastic Free-Context Grammar Based on Influence-Mapping

This paper presents a new system that solves the problem of finding suitable class schedule using strongly-typed heuristic search technique. The system is called Automated Timetabling Solver (ATTSolver). The system uses Stochastic Context-Free Grammar rules to build schedule and make use of influence maps to assign the fittest slot (place & time) for each lecture in the timetable. This system is very useful in cases of the need to find valid, diverse, suitable and on-the-fly timetable which takes into account the soft constraints that has been imposed by the user of the system. The performance of the proposed system is compared with the aSc system for the number of tested schedules and the execution time. The results show that the number of tested schedules in the proposed system is always less than that in aSc system. Moreover, the execution time of the proposed system is much better than aSc system in all cases of the sequential runs.

Experimental Evaluation of a New Apical Access and Closure Device

Transapical aortic valve implantation (TA-AVI) has evolved as a treatment option for high-risk patients who have severe aortic stenosis. The aim of this study was to evaluate the feasibility of a novel apical closure device to allow for standardized apical access and closure. The Apica ASC system consists of three components: an introducer system, a left ventricular low-profile titanium coil, and a closure cap. The ASC introducer system is fixed to the myocardium by anchoring the titanium coil into the epicardium. After the TA-AVI procedure, the closure cap is introduced through the system and delivered onto the titanium coil for final sealing. After sternotomy, fixation of the introducer system was successfully performed in an acute pig model. The apex was safely secured in all attempts, and the titanium coil created an effective seal around the Ascendra sheath. Finally, the closure cap was shown to be secure even when the hearts were pressurized to 200 mm Hg. Postmortem examination showed a uniform depth of the titanium coil through the endocardium into the myocardial wall without penetration into the left ventricular cavity. Apical access and closure is feasible using the sutureless Apica ASC device. The system seems to have the potential to further standardize the TA-AVI procedure, allowing wider applicability and more generalizability.

Comparative Evaluation of 18F-Labeled Glutamic Acid and Glutamine as Tumor Metabolic Imaging Agents

(18)F-labeled (2S,4R)-4-fluoro-l-glutamine (4F-GLN) has demonstrated high uptake in tumor cells that undergo high growth and proliferation. Similar tumor targeting properties have also been observed for (18)F-labeled (2S,4R)-4-fluoro-l-glutamate (4F-GLU), suggesting that both are useful imaging agents. A new labeling procedure facilitates the preparation of (18)F-(2S,4R)4F-GLN and (18)F-(2S,4R)4F-GLU with confirmed radiochemical and enantiomeric purity. Here, we report the preparation and comparative evaluation of (18)F-(2S,4R)4F-GLN and (18)F-(2S,4R)4F-GLU as tumor metabolic imaging agents. Uptake of enantiomerically pure (18)F-(2S,4R)4F-GLN and (18)F-(2S,4R)4F-GLU was determined in 3 tumor cell lines (9L, SF188, and PC-3) at selected time points. The in vitro cell uptake mechanism was evaluated by inhibition studies in 9L cells. In vivo biodistribution and PET studies were performed on male F344 rats bearing 9L tumor xenografts. In vitro cell uptake studies showed that (18)F-(2S,4R)4F-GLN displayed higher uptake than (18)F-(2S,4R)4F-GLU. Amino acid transport system ASC (alanine-serine-cysteine-preferring; in particular, its subtype ASCT2 [SLC1A5 gene]) and system X(c)(-) (SLC7A11 gene) played an important role in transporting (18)F-(2S,4R)4F-GLN and (18)F-(2S,4R)4F-GLU, respectively, across the membrane. After being transported into cells, a large percentage of (18)F-(2S,4R)4F-GLN was incorporated into protein, whereas (18)F-(2S,4R)4F-GLU mainly remained as the free amino acid in its original form. In vivo studies of (18)F-(2S,4R)4F-GLN in the 9L tumor model showed a higher tumor uptake than (18)F-(2S,4R)4F-GLU, whereas (18)F-(2S,4R)4F-GLU had a slightly higher tumor-to-background ratio than (18)F-(2S,4R)4F-GLN. Imaging studies showed that both tracers had fast accumulation in 9L tumors. Compared with (18)F-(2S,4R)4F-GLU, (18)F-(2S,4R)4F-GLN exhibited prolonged tumor retention reflecting its incorporation into intracellular macromolecules. Differences in uptake and metabolism in tumor cells were found between (18)F-(2S,4R)4F-GLN and (18)F-(2S,4R)4F-GLU. Both agents are potentially useful as metabolic tracers for tumor imaging.

Synthesis and evaluation of 18F labeled alanine derivatives as potential tumor imaging agents

This paper reports the synthesis and labeling of (18)F alanine derivatives. We also investigate their biological characteristics as potential tumor imaging agents mediated by alanine-serine-cysteine preferring (ASC) transporter system. Three new (18)F alanine derivatives were prepared from corresponding tosylate-precursors through a two-step labeling reaction. In vitro uptake studies to evaluate and to compare these three analogs were carried out in 9L glioma and PC-3 prostate cancer cell lines. Potential transport mechanisms, protein incorporation and stability of 3-(1-[(18)F]fluoromethyl)-L-alanine (L-[(18)F]FMA) were investigated in 9L glioma cells. Its biodistribution was determined in a rat-bearing 9L tumor model. PET imaging studies were performed on rat bearing 9L glioma tumors and transgenic mouse carrying spontaneous generated M/tomND tumor (mammary gland adenocarcinoma). New (18)F alanine derivatives were prepared with 7%-34% uncorrected radiochemical yields, excellent enantiomeric purity (>99%) and good radiochemical purity (>99%). In vitro uptake of the L-[(18)F]FMA in 9L glioma and PC-3 prostate cancer cells was higher than that observed for the other two alanine derivatives and [(18)F]FDG in the first 1h. Inhibition of cell uptake studies suggested that L-[(18)F]FMA uptake in 9L glioma was predominantly via transport system ASC. After entering into cells, L-[(18)F]FMA remained stable and was not incorporated into protein within 2h. In vivo biodistribution studies demonstrated that L-[(18)F]FMA had relatively high uptake in liver and kidney. Tumor uptake was fast, reaching a maximum within 30 min. The tumor-to-muscle, tumor-to-blood and tumor-to-brain ratios at 60 min post injection were 2.2, 1.9 and 3.0, respectively. In PET imaging studies, tumors were visualized with L-[(18)F]FMA in both 9L rat and transgenic mouse. L-[(18)F]FMA showed promising properties as a PET imaging agent for up-regulated ASC transporter associated with tumor proliferation.

Transport mechanisms of trans-1-amino-3-fluoro[1-14C]cyclobutanecarboxylic acid in prostate cancer cells

We investigated the mechanisms of trans-1-amino-3-fluoro[1-(14)C]cyclobutanecarboxylic acid (anti-[(14)C]FACBC) transport by human-derived prostate cancer (PCa) cells and normal human prostatic epithelial cells (PrECs). Using PCa cells (DU145, PC-3, LNCaP) and PrECs, we performed the following in vitro experiments: time-course, kinetics, competitive inhibition by synthetic/naturally occurring amino acids (AAs), exchange transport with synthetic/naturally occurring AAs and pH-dependency of anti-[(14)C]FACBC uptake. We also examined the amino acid transporter (AAT) expression using flow cytometry. The uptake of anti-[(14)C]FACBC by LNCaP and DU145 cells was higher than that by PC-3 and PrECs. The K(m) values for anti-[(14)C]FACBC were 64.4 and 191.7 μmol/L in the DU145 cells and PrECs, respectively. Total levels of anti-[(14)C]FACBC uptake were positively correlated with the expression level of system ASC in PCa cells. The contributions of Na(+)-dependent AATs to anti-[(14)C]FACBC uptake were greater than those of Na(+)-independent AATs, especially in PCa cells. In the presence of Na(+), glutamine and serine showed the strongest inhibitory effect against anti-[(14)C]FACBC uptake, suggesting that system ASC, especially ASCT2, is an important AAT for anti-[(14)C]FACBC. In contrast, phenylalanine and 2-amino-bicyclo[2,2,1]heptane-2-carboxylic acid, but not N-ethylmaleimide, almost completely inhibited the anti-[(14)C]FACBC uptake in the absence of Na(+), indicating the contribution of LAT1. In the exchange transport experiments, glutamine showed the strongest transstimulation of intracellular anti-[(14)C]FACBC efflux in DU145 cells. Furthermore, the contributions of Na(+)-independent AATs to the uptake of anti-[(14)C]FACBC in DU145 and PrECs were greater under acidic pH conditions than under neutral or alkaline pH conditions. Total uptake of anti-[(14)C]FACBC by PCa cells correlates with the expression level of system ASC in PCa cells. Furthermore, LAT1 is an important transport system for anti-[(14)C]FACBC uptake, especially in an acidic environment, such as the intra-tumoural environment.