The evaluation of TRACE/PARCS model for BWR-4 nuclear power plant by startup test transient analyses

Generally, the thermal hydraulic (TH) codes need the results of Neutron Kinetics (NK) codes providing the reactivity properties to calculate neutron flux. Then the TH codes perform the safety analyses obtaining the responses of pressure, temperature, or water level. Two kinds of different codes calculate different physical behaviors sequentially and separately. Simultaneously computing thermal hydraulic and neutron kinetics behaviors can enhance the accuracy of the analysis. Hence, it is crucial to develop the TH-NK coupled model. This study presents the capability of the TH-NK coupled model, developed by TRACE (TRAC/RELAP Advanced Computational Engine) and PARCS (Purdue Advanced Reactor Core Simulator), for the BWR-4 nuclear power plant. The establishment of the TRACE/PARCS model presented the nodal and component modeling methodologies. This model was used to simulate two startup tests of high power level system transients. Principal system responses, calculated by the TRACE/PARCS model, were compared with the measured data in startup tests and the results of the point kinetic calculation of the TRACE (TRACE/PK) to evaluate the model. The evaluation shows that the TRACE/PARCS model can simulate the interaction between thermal hydraulic and neutron kinetics phenomena and predict the transients suitably. Through the comparison, the TRACE/PARCS model can be confident doing the analyses of normal and abnormal operational transients to predict the transient responses.

Methodology for analyzing accidents with radioactive material release with code EPZDose

A methodology for analyzing accidents with radioactive material release with EPZDose code was established. This code assesses doses and it is designed and developed by NTHU (National Tsing Hua University). To confirm the capacity of EPZDose, three postulated accident scenarios Taiwanese NPPs Chinshan (BWR/4) and Maanshan (PWR) are analyzed. All these scenarios are SBO (station blackout) transients because it is assumed that they result in a release of radioactive material. In this study, the source term data for EPZDose are taken from MELCOR or RASCAL calculations. In addition, calculated results of RASCAL code are compared with the results of EPZDose for these scenarios. The comparison show that the EPZDose predictions are consistent with the data of RASCAL. This indicates that the EPZDose has a respectable accuracy in the analysis of radioactive material release accidents.

LOCA analysis of BWR-4/Mark-I nuclear power plant with TRACE

This study established an RCS-Containment coupled model that integrates the reactor coolant system (RCS) and the containment system by using the TRACE code. The coupled model was used in both short-term and long-term loss of coolant accident (LOCA) analyses. Besides, the RELAP5/CONTAN model that only contains the containment system was also developed for comparison. For short-term analysis, three kinds of LOCA scenarios were investigated: the recirculation line break (RCLB), the main steam line break (MSLB), and the feedwater line break (FWLB). For long-term analysis, the dry-well and suppression pool temperature responses of the RCLB were studied. The analysis results of RELAP5/CONTAN and TRACE models are benchmarked with those of FSAR and RELAP5/GOTHIC models, and it appears that the results of the above four models are consistent in general trends.

The core shroud leakage analysis and study for Kuosheng nuclear power plant

Kuosheng Nuclear Power Plant (NPP) is a BWR/6 plant in Taiwan. First, this study focuses on the establishment of the TRACE/SNAP model for Kuosheng. To check the system response of the Kuosheng TRACE/SNAP model, the Final Safety Analysis Report (FSAR) and startup tests data are used to assess the TRACE/SNAP model. The TRACE predictions are consistent with the FSAR and startup tests data. This indicates that there is a respectable accuracy in the TRACE/SNAP model of Kuosheng NPP. Second, this study also focuses on the application of the TRACE/SNAP model in the core shroud leakage. The Kuosheng NPP TRACE/SNAP model is used to perform the analysis of core shroud leakage. The TRACE results imply that Kuosheng NPP is in a safe situation when the core shroud leakage transient occurs.

The simulation and study of ELAP event with URG and FLEX mitigation strategies for PWR by using TRACE code

In this research, TRACE code with the interface SNAP was used to evaluate and simulate the postulated Extended Loss of AC Power (ELAP) accident in Maanshan Nuclear Power Plant (NPP). This study is to determine whether Reactor Coolant System (RCS) water level will be below Top of Active Fuel (TAF) while the 5th diesel generator and gas turbines are all disabled when the accident occurred. The scenario and assumptions of postulated ELAP in this research are referred to the WCAP-17601-Pt and NUREG-1953 reports. Additionally, this study will run a base case without any mitigation strategy and four cases with multiple mitigation strategies to analyze the effectiveness of URG and FLEX strategies. According to the analysis results of TRACE, it can be found that all four cases with mitigation strategies can keep RCS water level above TAF. This indicates that URG and FLEX strategies can ensure the safety function of reactor.

Evaluation of control room habitability in case of LOCA for Maanshan NPP using codes RADTRAD, HABIT and ALOHA

The method for the evaluation of the control room habitability is presented in this paper with focus on Maanshan PWR nuclear power plant (NPP) using the codes RADTRAD, HABIT, and ALOHA. Therefore, this paper is divided into two parts: The first part is the evaluation of the cumulative dose at the control room, the exclusion area boundary (EAB) and the low population zone (LPZ) in case of an design basis loss of coolant accident (DBA/LOCA). For this first part, the Maanshan NPP models of the code RADTRAD/SNAP were used for the analysis. The second part is the evaluation of the control room habitability under the assumption of CO2 storage burst. For this part, the HABIT and ALOHA codes were used. As result it was seen that the RADTRAD calculation results are below the failure criteria of standard review plan (SRP) and 10 CFR 100.11. The HABIT and ALOHA results are below the R.G. 1.78 failure criteria. These results indicate that Maanshan NPP’ habitability can be maintained under the above conditions.

Nanoparticle distribution during systemic inflammation is size-dependent and organ-specific

This study comprehensively investigates the changing biodistribution of fluorescent-labelled polystyrene latex bead nanoparticles in a mouse model of inflammation. Since inflammation alters systemic circulatory properties, increases vessel permeability and modulates the immune system, we theorised that systemic inflammation would alter nanoparticle distribution within the body. This has implications for prospective nanocarrier-based therapies targeting inflammatory diseases. Low dose lipopolysaccharide (LPS), a bacterial endotoxin, was used to induce an inflammatory response, and 20 nm, 100 nm or 500 nm polystyrene nanoparticles were administered after 16 hours. HPLC analysis was used to accurately quantify nanoparticle retention by each vital organ, and tissue sections revealed the precise locations of nanoparticle deposition within key tissues. During inflammation, nanoparticles of all sizes redistributed, particularly to the marginal zones of the spleen. We found that LPS-induced inflammation induces splenic macrophage polarisation and alters leukocyte uptake of nanoparticles, with size-dependent effects. In addition, spleen vasculature becomes significantly more permeable following LPS treatment. We conclude that systemic inflammation affects nanoparticle distribution by multiple mechanisms, in a size dependent manner.

The ultimate response guideline simulation and analysis by using TRACE for Lungmen ABWR nuclear power plant

In this research, the TRACE/SNAP model of Lungmen ABWR nuclear power plant (NPP) has been established for the simulation and analysis of ultimate response guideline (URG). The main actions of URG are depressurization and low pressure water injection of reactor and containment venting. This research focuses to assess the URG utility of Lungmen NPP under Fukushima-like conditions. This study consists of three steps. The first step is the establishment of Lungmen NPP TRACE/SNAP model. In order to evaluate the system response of TRACE/SNAP model, FSAR data (MSIV closure and loss of feedwater flow transient) were used to compare with the results of TRACE. The second step is the URG simulation and analysis under Fukushima-like conditions by using Lungmen NPP TRACE/SNAP model. In this step, the no URG case was also performed in order to evaluate the URG effectiveness of Lungmen NPP. In order to confirm the mechanical property and integrity of fuel rods, the final step is FRAPTRAN analysis. According to TRACE analysis results, the URG can keep the peak cladding temperature (PCT) below the criteria 1 088.7 K under Fukushima-like conditions which indicates that Lungmen NPP can be controlled in a safe situation. Nevertheless, if Lungmen NPP does not perform the URG under Fukushima-like conditions, the water level may drop lower than TAF after 1 100 s which means a safety issue about the fuel rods may be generated. The analysis results of FRAPTRAN also indicate the integrity of fuel rods cannot be kept under the above conditions.

Promoted decomposition of NOx in automotive diesel-like exhausts by electro-catalytic honeycombs

NO and NO2 (collectively called NOx) are major air pollutants in automotive emissions. More effective and easier treatments of NOx than those achieved by the present methods can offer better protection of human health and higher fuel efficiency that can reduce greenhouse gas emissions. However, currently commercialized technologies for automotive NOx emission control cannot effectively treat diesel-like exhausts with high NOx concentrations. Thus, exhaust gas recirculation (EGR) has been used extensively, which reduces fuel efficiency and increases particulate emission considerably. Our results show that the electro-catalytic honeycomb (ECH) promotes the decomposition of NOx to nitrogen and oxygen, without consuming reagents or other resources. NOx can be converted to nitrogen and oxygen almost completely. The ECHs are shown to effectively remove NOx from gasoline-fueled diesel-like exhausts. A very high NO concentration is preferred in the engine exhaust, especially during engine cold-start. Promoted NOx decomposition (PND) technology for real-world automotive applications is established in this study by using the ECH. With PND, EGR is no longer needed. Diesel-like engines can therefore achieve superior fuel efficiency, and all major automotive pollutants can be easily treated due to high concentration of oxygen in the diesel-like exhausts, leading to zero pollution.

Evaluations of the CCFL and critical flow models in TRACE for PWR LBLOCA analysis

This study aims to develop the Maanshan Pressurized Water Reactor (PWR) analysis model by using the TRACE (TRAC/RELAP Advanced Computational Engine) code. By analyzing the Large Break Loss of Coolant Accident (LBLOCA) sequence, the results are compared with the Maanshan Final Safety Analysis Report (FSAR) data. The critical flow and Counter Current Flow Limitation (CCFL) play an important role in the overall performance of TRACE LBLOCA prediction. Therefore, the sensitivity study on the discharge coefficients of critical flow model and CCFL modeling among different regions are also discussed. The current conclusions show that modeling CCFL in downcomer has more significant impact on the peak cladding temperature than modeling CCFL in hot-legs does. No CCFL phenomena occurred in the pressurizer surge line. The best value for the multipliers of critical flow model would be 0.5 and the TRACE could consistently predict the break flow rate in the LBLOCA analysis as shown in FSAR.

The development and assessment of TRACE model for Lungmen ABWR

For the nuclear power plant Lungmen (two blocks of Advanced Boiling Water Reactor (ABWR)) in Taiwan a plant model for the thermal hydraulic program TRACE (TRAC/RELAP Advanced Computational Engine) was developed. This model is and will be used for the simulation of normal and anomalous plant behaviour as well as for the simulation of incident scenarios. The presentation of this model is done in three steps: The first step is the development of a TRACE model of Lungmen nuclear power plant (NPP) which includes the vessel, the main steam lines and important control systems (such as the feedwater control system, recirculation flow control system, etc.). Key parameters were identified to refine the model further in the frame of a steady state analysis. The second step is the performance of TRACE transient analyses, such as MSIV closure direct scram (MSIVCD, MSIV = Main Steamline Isolation Valve) and loss of feedwater flow (LOFW). The above transient data of Final Safety Analysis Report (FSAR) are used to verify the Lungmen NPP TRACE model. The trends of their analysis results are roughly similar. It indicates that TRACE model is satisfying for the purpose of Lungmen NPP safety analyses. The third step is the prediction analysis of Lungmen NPP startup tests by using the TRACE model. The prediction analysis results of TRACE comply with the startup tests procedure criteria.

Effects of phenol feeding pattern on microbial community structure and cometabolism of trichloroethylene

Cometabolism of trichloroethylene (TCE) by phenol-fed enrichments was evaluated in four reactors with distinct phenol feeding patterns. The reactors were inoculated from the same source, operated at the same average dilution rate, and received the same mass of phenol over time. Only the timing of phenol addition differed. Reactor C received phenol continuously; reactor SC5 received phenol semicontinuously--alternating between 5 h of feed and 3 h without feed; reactor SC2 alternated between 2 h of feed and 6 h without feed; and reactor P received a single pulse every 24 h. The structure of the enrichments and their capacity for TCE transformation were analyzed. In long-term operation, reactors C and SC5 were dominated by fungi, had higher levels of predators, were more susceptible to biomass fluctuations, and exhibited reduced capacity for TCE transformation. Reactors P and SC2 were characterized by lower levels of fungi, higher bacterial biomass, higher concentrations of TCE-degrading organisms, and higher rates of TCE transformation. After 200 days of operation, rates of TCE transformation increased 10-fold in reactor P, resulting in TCE transformation rates that were 20 to 100 times higher than the rates of the other reactor communities. The cause of this shift is unknown. Isolates capable of the highest rates of TCE transformation were obtained from reactor P. We conclude that cometabolic activity depends upon microbial community structure and that the community structure can be manipulated by altering the growth substrate feeding pattern.

Fabrication of high aspect-ratio polymer microstructures for large-area electronic portal x-ray imagers

Megavoltage x-ray imaging performed during radiotherapy is the method of choice for geometric verification of patient localization and dose delivery. Presently, such imaging is increasingly performed using electronic portal imaging devices (EPIDs) based on indirect detection active matrix flat panel imagers (AMFPIs). These devices use a scintillating phosphor screen in order to convert incident x-rays into optical photons, which are then detected by the underlying active matrix photodiode array. The use of a continuous phosphor introduces a trade-off between x-ray quantum efficiency and spatial resolution, which limits current devices to use only ∼2% of the incident x-rays. This trade-off can be circumvented by "segmented phosphor screens", comprising a two-dimensional matrix of optically-isolated cell structures filled with scintillating phosphor. In this work we describe the fabrication of millimeter-thick segmented phosphor screens using the MEMS (micro-electro-mechanical-system) polymer SU-8. This method is capable of being extended to large-area substrates.

AAV-mediated delivery of interferon-β for the treatment of retinoblastoma in preclinical models

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Background: Interferon-β has anti-tumor properties against a variety of malignancies through direct cytotoxicity as well as immunological effects. In order to circumvent limitations of IFN-β therapy, we have developed an adeno-associated viral gene therapy approach to deliver IFN-β directly to tumors. In this study, we tested the efficacy of AAV mediated delivery of IFN-β in preclinical retinoblastoma models. Retinoblastoma is an ideal candidate for gene-therapy based anti-cancer treatments because viral infection and IFN-β delivery can be contained within the ocular environment thereby minimizing systemic toxicity. Methods: Retinoblastoma cell lines Weri and Y79 were treated in vitro with recombinant human Interferon-β and then subjected to Viacount assays, Nexin apoptosis assays, FACS cell cycle analysis, and immunolabeling for proliferation (BrdU) and apoptosis (caspase and TUNEL). An orthotopic Xenograft retinoblastoma rat model with luciferase reporter were established and treated with single subconjunctival injection of AAV-IFN-β gene therapy. Xenogen in vivo imaging was used to follow tumor volume. Blood and tissue samples (ELISA) were obtained to determine IFN-β levels. Results: Weri and Y79 cells showed maximum reduction in viability at 500 IU/ml and 2500 IU/ml respectively. Weri response was found to be cell death by Caspase and TUNEL assay. Y79 response was found to be due to suppression of proliferation as measured by BrdU incorporation and cell cycle analysis. In the retinoblastoma xenograft model there was no increase in tumor volume by serial in vivo imaging compared to control animals. Stable levels of IFN-β were maintained at 20 ng/ml >6weeks following injection. Plasma levels were undetectable 42 days following treatment. Conclusions: Retinoblastoma cell lines exhibit pleiotropic responses to IFN-β consistent with previous studies. Intravitreal injection of AAV-IFN-β resulted in efficient retinal infection and sustained IFN-β production. Viral spread outside of the eye was not detected. Using our retinoblastoma xenograft model we found that intravitreal injection of AAV-IFN-β had a potent anti-tumor effect in vivo. These data suggest that AAV mediated delivery of IFN-β may provide a complementary approach to systemic chemotherapy.

No significant financial relationships to disclose.

Inhibition of glycinamide ribonucleotide formyltransferase results in selective inhibition of macrophage cytokine secretion in vitro and in vivo efficacy in rat adjuvant arthritis

OBJECTIVE

To determine the effects of a glycinamide ribonucleotide formyltransferase (GARFT) inhibitor on macrophage inflammatory processes and in vivo in rat adjuvant arthritis.

METHODS

GARFT inhibitors, LY309886 (6S-2',5'-thienyl-5, 10-dideazatetrahydrofolic acid) and LY329201 (R)-N-[[5-[2-(2-amino-1,4,5,6,7,8-hexahydro-4-oxopyrido[2,3-d]pyrimidin-6-yl)ethyl]-2-thienyl]carbonyl]-L-glutamatic acid disodium salt, were investigated in vitro and ex vivo on primary murine peritoneal macrophages and in the RAW macrophage cell line for both purine depletion and inhibition of LPS induced monokine secretion. In vivo efficacy following GARFT inhibition was evaluated in modified rat adjuvant arthritis.

RESULTS

LY309886 inhibited purine biosynthesis in the RAW cell line with an EC50 of 90 nM, an effect readily reversible with exogenous hypoxanthine. LY309886 and LY329201 also inhibited LPS induced TNF alpha and MIP1 alpha in these cells and in primary macrophages. A similar effect could be demonstrated ex vivo with mice dosed for two days with 3 mg/kg of LY329201. LY329201 as well as methotrexate demonstrated a dose dependent reduction in both paw and spleen weight and improved joint histology following 2 weeks of dosing in a rat adjuvant arthritis study.

CONCLUSION

These results suggest that GARFT inhibitors should be tested in the treatment of rheumatoid arthritis by considering their mechanism of action, here successfully tested on activated macrophages.

Antiangiogenic and antitumor effects of a protein kinase Cbeta inhibitor in murine lewis lung carcinoma and human Calu-6 non-small-cell lung carcinoma xenografts

In cell culture, the compound 317615.2HCl, a potent inhibitor of VEGF-stimulated HUVEC proliferation, was not very effective against Calu-6 non-small-cell lung carcinoma cells (IC50 26 microM). Exposure to combinations of paclitaxel or carboplatin and 317615.2HCl with Calu-6 cells in culture resulted in cell survival that reflected less-than-additivity to additivity of the two agents. Administration of 317615.2HCl orally twice daily to nude mice bearing subcutaneous Calu-6 tumors resulted in a decreased number of intratumoral vessels as determined by CD31 and CD105 staining to 50% of the number in control tumors. 317615.2HCl showed antitumor activity against the Lewis lung carcinoma and increased the tumor growth delay produced by paclitaxel by 5-fold, that produced by gemcitabine by 2-fold and that produced by carboplatin by 1.7-fold. There was a decrease in the number of lung metastases in the Lewis lung carcinoma that paralleled the increased response of the primary tumor with each treatment combination. Administration of 317615.2HCl also increased the tumor growth delay produced by fractionated radiation therapy in the Lewis lung tumor. Treatment with 317615.2HCl was an effective therapy in the Calu-6 non-small-cell lung carcinoma xenograft when the compound was administered early (days 4-18) or later (days 14-30). Combination treatment regimens in which 317615.2HCl was administered along with or sequentially with paclitaxel or carboplatin were much more effective than the chemotherapeutic agents administered alone. 317615.2HCl is in early clinical testing.

Presentation of striatal hyperintensity on T1-weighted MRI in patients with hemiballism-hemichorea caused by non-ketotic hyperglycemia: report of seven new cases and a review of literature

Recent studies have shown unique clinicoradiologic characteristics in patients with hemiballism-hemichorea (HB-HC) caused by non-ketotic hyperglycemia; however, there is still a limited number of patients being reported. We report 7 patients (3 males and 4 females) with this type of dyskinesia, whose ages ranged from 60 to 84 years. Brain CT of these patients showed hyperdensity in the contralateral striatum, corresponding with MRI studies that showed an increased signal intensity on T1-weighted images and a decreased signal on T2-weighted images. After metabolic control had been achieved, the hyperkinetic state of these patients abruptly ceased. Follow-up neuroimaging studies in 2 patients documentied complete resolution of the striatal hyperintensity on brain CT and MRI after 3 months and 6 months, respectively. A review of patients with HB-HC caused by non-ketotic hyperglycemia reported formerly and in the present study shows that the dyskinesia tends to occur in aged diabetic patients. The age of patients with dyskinesia secondary to cerebral infarction is generelly much lower. We also found that 86% (30 out of 35 cases) patients reported with HB-HC caused by non-ketotic hyperglycemia were Asians. The prognosis of the dyskinesia was excellent, and the radiological abnormalities are completely reversible.

Cryptophycins: a novel class of potent antimitotic antitumor depsipeptides

The antitumor cryptophycins are synthetic derivatives of the desipeptide cryptophycins isolated from the cyanobacterium Nostoc sp. Cryptophycin 52 that is currently in clinical trial in solid tumors, is prepared by total synthesis of four key fragments that are coupled to form the final product. The mechanism of anticancer activity of the cryptophycins has been associated with their destabilization of microtubules and with their induction of bcl-2 phosphorylation leading to apoptosis. The cryptophycins maintain activity against ovarian and breast carcinoma cells that overexpress the multidrug resistance efflux pump P-glycoprotein. Cryptophycin 52 has demonstrated a broad range of antitumor activity against both murine and human tumors. In the human MX-1 breast carcinoma xenograft cryptophycin 55 produced greater-than- additive tumor response in combination with 5-fluorouracil. In human non-small cell lung carcinoma and human small cell carcinoma xenografts, administration of the cryptophycins along with gemcitabine, cisplatin or carboplatin resulted in antitumor activity greater than either agent alone. The cryptophycins appear to be additive with fractionated radiation therapy in the human H460 non-small cell lung carcinoma. In the human HCT116 colon carcinoma, the cryptophycins resulted in a greater than additive tumor response when administered sequentially with 5-fluorouracil or irinotecan. Treatment of animals bearing intraperitoneal human OVCAR-2 ovarian carcinoma with cryptophycin 52 resulted in survival times that were greater than those achieved with docetaxel or paclitaxel. Cryptophycin 52 is currently in early clinical testing.

Antiangiogenic and antitumor effects of a protein kinase Cbeta inhibitor in human HT-29 colon carcinoma and human CaKi1 renal cell carcinoma xenografts

The compound 317615 x 2HCl, a selective protein kinase Cbeta inhibitor, was not very cytotoxic toward human CaKi1 renal cell carcinoma cells or human HT-29 colon carcinoma cells in monolayer culture. Isobologram analysis was used to determine additivity or synergy of the combination regimens. Exposure of CaKi1 cells to 317615 x 2HCl (10 or 100 mM) along with gemcitabine or 5-fluorouracil for 24 hours resulted in cytotoxicity that appeared to be less-than-additive to additive for the two agents. Exposure of HT-29 cells to gemcitabine along with 317615 x 2HCl (10 mM or 100 mM) resulted in a synergistic cytotoxicity while combinations with 5-fluorouracil resulted in additive to greater-than-additive cytotoxicity for the agents. After treatment of CaKi1 or HT-29 xenograft-bearing mice with 317615 x 2HCl, immunohistochemical staining for expression of endothelial specific markers, either CD31 or CD105, was used to quantify the number of intratumoral vessels in the samples. CaKi1 tumor angiogenesis was very responsive to treatment with 317615 x 2HCl such that the number of intratumoral vessels stained by CD31 or CD105 was decreased to 20% of the control. The HT-29 colon carcinoma angiogenesis was also responsive to 317615 x 2HCl, such that the number of intratumoral vessels stained by CD31 or CD105 was decreased to 40% to 50% of the controL 5-fluorouracil, cisplatin or fractionated radiation therapy was combined with treatment with 317615 x 2HCl in the simultaneous combination treatment regimen in animals bearing HT-29 colon carcinoma xenografts. The resulting tumor growth delays indicated that administration of 317615 x 2HCl increased the effects of the cytotoxic therapy. Both a simultaneous or an overlapping treatment regimen and a sequential treatment regimen were used to assess 317615 x 2HCl alone and along with fractionated radiation therapy or gemcitabine against the human CaKi1 renal cell carcinoma xenograft. The CaKi1 tumor was quite sensitive to fractionated radiation therapy and to gemcitabine and, although 317615 x 2HCl was an effective single agent in this tumor, the combination regimens did not reach additivity for the combination regimens in vivo. 317615 x 2HCl is in early clinical testing.

Trophic conversion of an obligate photoautotrophic organism through metabolic engineering

Most microalgae are obligate photoautotrophs and their growth is strictly dependent on the generation of photosynthetically derived energy. We show that the microalga Phaeodactylum tricornutum can be genetically engineered to thrive on exogenous glucose in the absence of light through the introduction of a gene encoding a glucose transporter (glut1 or hup1). This demonstrates that a fundamental change in the metabolism of an organism can be accomplished through the introduction of a single gene. This also represents progress toward the use of fermentation technology for large-scale commercial exploitation of algae by reducing limitations associated with light-dependent growth.

Biodegradable block copolymers for delivery of proteins and water-insoluble drugs

Release of several drugs from new ABA-type biodegradable thermal gels, ReGel, including proteins and conventional molecules, are presented. These are biodegradable, biocompatible polymers that demonstrate reverse thermal gelation properties. Organic solvents are not used in the synthesis, purification, or formulation of these polymers. The unique characteristics of ReGel hinge on the following two key properties: (1) ReGel is a water soluble, biodegradable polymer at temperatures below the gel transition temperature; (2) ReGel forms a water-insoluble gel once injected. This is consistent with a hydrophobically bonded gel state where all interactions are physical, with no covalent crosslinking. An increase in viscosity of approximately 4 orders of magnitude accompanies the sol--gel transition. The gel forms a controlled release drug depot with delivery times ranging from 1 to 6 weeks. ReGel's inherent ability to solubilize (400 to >2000-fold) and stabilize poorly soluble and sensitive drugs, including proteins is a substantial benefit. The gel provided excellent control of the release of paclitaxel for approximately 50 days. Direct intratumoral injection of ReGel/paclitaxel (OncoGel) results in a slow clearance of paclitaxel from the injection site with minimal distribution into any organ. Efficacies equivalent to maximum tolerated systemic dosing were observed at OncoGel doses that were 10-fold lower. Data on protein release (pGH, G-CSF, insulin, rHbsAg) and polymer biocompatibility are discussed.

Antiangiogenic and antitumor effects of a protein kinase C beta inhibitor in human hepatocellular and gastric cancer xenografts

Hepatocellular carcinoma and gastric cancer are the most prevalent tumors worldwide. Hep3B hepatocellular carcinoma and HS746T gastric cancer were used as models for these diseases in culture and in vivo. The PKC beta inhibitor 317615.2HCl was not very cytotoxic toward HS746T or Hep3B cells in culture and was, in the main, additive in cytotoxicity with cisplatin, 5-fluorouracil and gemcitabine when cell in monolayer were exposed to these agents in combination with 317615.2HCl. Treatment of nude mice bearing HS746T or Hep3B xenografts with 317615.2HCl orally twice daily resulted in a small decreased in CD31-stainable intratumoral vessels in the HS746T tumors and 60% decrease in CD31-stainable vessels in the Hep3B tumors. Somewhat larger decreases were observed in the vessel stained with CD105. As a single agent 317615.2HCl produced tumor growth delays between 6.5 and 15 days in the HS746T xenograft and between 5 and 25 days in the Hep3B xenograft over the dosage range (3 to 30 mg/kg). Sequential and simultaneous combinations with 317615.2HCl and 5-fluorouracil and gemcitabine resulted in increases in tumor growth delay on both schedules. Gemcitabine produced a 15-day tumor growth delay of the HS746T gastric carcinoma that was increased to 40 days when combined simultaneously with 317615.2HCl and to 30 days with the sequential treatment regimen. 5-Fluorouracil produced a 9-day tumor growth delay of the Hep3B hepatocellular carcinoma that increased to 31 days by simultaneous treatment with 317615.2HCl and to 43 days with the sequential treatment regimen. Treatment with the protein kinase C beta inhibitor 317615.2HCl decreased HS746T and Hep3B angiogenesis and improved treatment outcome with 5-fluorouracil and gemcitabine.

Cryptophycin-induced hyperphosphorylation of Bcl-2, cell cycle arrest and growth inhibition in human H460 NSCLC cells

Bcl-2 has been described as a factor that can protect from apoptosis. The protective effect of Bcl-2 may be lost if the protein is phosphorylated. Bcl-2 phosphorylation can be induced by agents that affect microtubule depolymerization or prevent microtubule assembly. In 13 human tumor cell lines there was a high degree of heterogeneity in Bcl-2 protein expression. Human H460 non-small-cell lung carcinoma (NSCLC) cells expressed high levels of Bcl-2 and were selected for study. Western blot analysis for Bcl-2 phosphorylation was carried out after 4 h and 24 h of exposure to cryptophycin 52, cryptophycin 55, paclitaxel or vinblastine. Cryptophycin 52 and cryptophycin 55 were very potent inducers of Bcl-2 phosphorylation. After 4 h of exposure, Bcl-2 phosphorylation was evident with 0.05 nM cryptophycin 52, 0.25 nM cryptophycin 55, 5 nM vinblastine and 50 nM paclitaxel. The hyperphosphorylated form of Bcl-2 was evident after 24 h exposure of H460 cells to 0.25 nM cryptophycin 52 or cryptophycin 55 and 50 nM vinblastine or paclitaxel. The effects of the compounds on the cell cycle paralleled those on Bcl-2 phosphorylation. In H460 cells 90% cell killing was obtained with 0.13 nM cryptophycin 52, 0.2 nM cryptophycin 55, 20 nM paclitaxel and > 100 nM vinblastine after 24 h of exposure as determined by colony formation. In Bcl-2-negative Calu-6 NSCLC cells, 90% cell killing was obtained with 0.03 nM cryptophycin 52, 0.1 nM cryptophycin 55, 11 nM paclitaxel and 0.5 nM vinblastine using the same experimental design. Thus, cryptophycins are potent inducers of Bcl-2 phosphorylation. The cryptophycins were more potent cytotoxic agents in Bcl-2-negative Calu-6 cells than in Bcl-2-positive H460 cells indicating that pathways triggered by Bcl-2 phosphorylation are involved in cryptophycin-induced lethality.

Antiangiogenic and antitumor effects of a protein kinase Cbeta inhibitor in human T98G glioblastoma multiforme xenografts

Although rare, the morbidity and mortality from brain tumors are significant. Chemotherapy has made only a small impact on these tumors. The human T98G glioblastoma multiforme cell line was used as a brain tumor model. The protein kinase Cbeta inhibitor 317615 x 2HCl was not highly cytotoxic toward T98G cells in culture and was additive in cytotoxicity with carmustine (BCNU). When nude mice bearing s.c. T98G tumors were treated with 317615 x 2HCl p.o. twice daily on days 14-30 after tumor cell implantation, the number of intratumoral vessels stained by CD31 was decreased to 37% of control, and the number of intratumoral vessels stained by CD105 was decreased to 50% of control. The compound 317615 x 2HCl was an active antitumor agent against s.c. growing T98G xenografts. A treatment regimen administering 317615 x 2HCl before, during, and after BCNU was compared with a treatment regimen administering 317615 x 2HCl sequentially after BCNU. In the tumor growth delay determination of the s.c. tumor, the sequential treatment regimen was more effective than the simultaneous treatment regimen. However, when the same treatments were administered to animals bearing intracranial T98G tumors, the survival of animals receiving the simultaneous treatment regimen increased from 41 days for those treated with BCNU alone to 102 days for animals treated with the combination, whereas animals receiving the sequential treatment regimen survived 74 days. Treatment with the protein kinase Cbeta inhibitor decreased T98G glioblastoma multiforme angiogenesis and improved treatment outcome with BCNU.

Expression of pRB, cyclin/cyclin-dependent kinases and E2F1/DP-1 in human tumor lines in cell culture and in xenograft tissues and response to cell cycle agents

PURPOSE

Cell cycle regulatory components are interesting targets for cancer therapy. Expression of pRb, cyclin D1, cdk4, cyclin E, cdk2, E2F1 and DP-1 was determined in MCF-7 and MDA-MB-468 breast carcinoma cells, H460 and Calu-6 non-small cell lung carcinoma cells, H82 and SW2 small cell lung carcinoma cells, HCT116 and HT29 colon carcinoma cells and LNCaP and DU-145 prostate carcinoma cells.

METHODS

For Western blotting, the ratio with actin expression was used to normalize the data; all lines were run on the same gels.

RESULTS

In cell culture, pRb was not detected in MB-468 and H82 was low in SW2 and DU-145 and highest in HCT116; in tumors, pRb was not detected in MB-468, H82, SW2, and DU-145 and was highest in LNCaP and Calu-6. Cyclin D1 was not detected in SW2 cells in culture, was low in MB-468 and H82, and was highest in LNCaP and H460; in tumors, cyclin D1 was low in MB-468, H460, SW2 and DU 145, and was highest in LNCaP. In cell culture, cdk4 was lowest in Calu-6, HCT116, HT29 and DU-145 and highest in H82 and SW2; in tumors, cdk4 was low in MCF-7, MB-468, H460, Calu-6 and HCT116 and was very high in the SW2. Expression of cyclin E was very low in MCF-7 and HT29 and high in H460 in culture and was very low in MCF-7, H460, Calu-6, H82, HT29 and DU-145 in tumors and high in HCT116 and LNCaP. In cell culture, E2F1 was lowest in MB-468, Calu-6, HT29 and DU-145 cells and highest in LNCaP cells; in tumors, E2F1 was lowest in MCF-7, MB-468 and Calu-6 and highest in LNCaP. In cell culture, DP-1 was lowest in MB-468, HCT116 and HT29 and highest in SW2. The MCF-7 and MB-468 lines were most resistant to flavopiridol and olmoucine and the H460 and Calu-6 lines were most resistant to genistein. The SW2 tumor was most responsive to flavopiridol and olomoucine.

CONCLUSIONS

There is a high degree of variability in the expression of cell cycle components in human tumor cell lines, resulting in complexity in predicting response to cell cycle directed agents.

Photoprotection in a zeaxanthin- and lutein-deficient double mutant of Arabidopsis

When light absorption by a plant exceeds its capacity for light utilization, photosynthetic light harvesting is rapidly downregulated by photoprotective thermal dissipation, which is measured as nonphotochemical quenching of chlorophyll fluorescence (NPQ). To address the involvement of specific xanthophyll pigments in NPQ, we have analyzed mutants affecting xanthophyll metabolism in Arabidopsis thaliana. An npq1 lut2 double mutant was constructed, which lacks both zeaxanthin and lutein due to defects in the violaxanthin de-epoxidase and lycopene in-cyclase genes. The npq1 lut2 strain had normal Photosystem II efficiency and nearly wild-type concentrations of functional Photosystem II reaction centers, but the rapidly reversible component of NPQ was completely inhibited. Despite the defects in xanthophyll composition and NPQ, the npq1 lut2 mutant exhibited a remarkable ability to tolerate high light.

Interaction of the antitumor compound cryptophycin-52 with tubulin

Cryptophycin-52 (LY355703) is currently undergoing clinical evaluation for cancer chemotherapy. It is a potent suppressor of microtubule dynamics in vitro, and low picomolar concentrations appear to inhibit cancer cell proliferation at mitosis by stabilizing spindle microtubules. In the present study, using [(3)H]cryptophycin-52, we found that the compound bound to tubulin at a single high-affinity site [apparent K(a) (3.6 +/- 1) x 10(6) L/mol, 34 degrees C]. The binding of cryptophycin-52 to tubulin was rapid, not appreciably temperature-dependent, and very poorly reversible. However, we could remove [(3)H]cryptophycin-52 from [(3)H]cryptophycin-52-tubulin complex by denaturing the complex with either urea treatment or boiling. These data suggest that the binding of cryptophycin-52 to tubulin is not covalent. A van't Hoff plot of the binding data indicated that the binding of cryptophycin-52 to tubulin is primarily entropy-driven with a minimum enthalpy contribution. In addition, cryptophycin-52 perturbed the far-ultraviolet circular dichroic spectrum of tubulin and it inhibited the colchicine-induced guanosine triphosphatase activity of tubulin, indicating that its binding to tubulin induces a conformational change in the tubulin. Competition experiments with vinblastine suggest that the binding site for crytophycin-52 may overlap with the vinblastine binding site.

Low-level secretion of human hepatitis B virus virions caused by two independent, naturally occurring mutations (P5T and L60V) in the capsid protein

The functional significance of naturally occurring variants of human hepatitis B virus (HBV) remains largely unknown. Previously, we reported an immature secretion phenotype caused by a highly frequent mutation at amino acid 97 of the HBV core (capsid) protein (HBcAg). This phenotype is characterized by a nonselective and excessive secretion of virions containing an immature genome of single-stranded viral DNA. To extend our study of virion secretion to other naturally occurring variants, we have characterized mutations at HBcAg codons 5, 38, and 60 via site-directed mutagenesis. Although the phenotype of the mutation at codon 38 is nearly identical to that for the wild-type virus, our study reveals that a single mutation at codon 5 or 60 exhibits a new extracellular phenotype with significantly reduced virion secretion yet maintains normal intracellular viral DNA replication. A complementation study indicates that the mutant core protein alone is sufficient for the "low-secretion" phenotype. Furthermore, the low-secretion phenotype of the codon 5 mutant appears to be induced by the loss of a parental proline residue, rather than by the gain of a new amino acid. Our study underscores the core protein as another crucial determinant in virion secretion, in addition to the known envelope proteins. Our present results suggest that a very precise structure of both alpha-helical and nonhelical loop regions of the entire HBcAg molecule is important for virion secretion. The low-secretion variants may contribute to the phenomenon of gradually decreasing viremia in chronic carriers during the late phase of persistent infection.

Antitumor activity of cryptophycins: effect of infusion time and combination studies

INTRODUCTION/PURPOSE

Cryptophycins are a family of antitubulin antitumor agents. A synthetic cryptophycin derivative (LY355703, CRYPTO 52) is in early clinical evaluation. The effect of infusion time on the antitumor activity of four cryptophycins was assessed in rats bearing the 13762 mammary carcinoma and combination treatment regimens were assessed in nude mice bearing human tumor xenografts.

METHODS

The cryptophycins were prepared in 2% PEG300/8% cremophor/90% normal saline and delivered by jugular vein catheter on days 7, 9 and 11 post tumor implant to 13762 tumor-bearing rats. The cryptophycins prepared in the same formulation were administered by intravenous bolus injection on an alternate day schedule for five doses to human tumor xenograft bearing nude mice.

RESULTS

An infusion time of 2 h in the rats increased the tumor growth delay produced by CRYPTO 52 and CRYPTO 55, while increasing the infusion time to 6 h continued to increase the tumor growth delay for CRYPTO 292 and CRYPTO 296. Administering CRYPTO 292 at a higher dose two times was more effective than administering it at a lower dose three times. The tumor growth delays produced by the cryptophycins in the rat 13762 mammary carcinoma were greater than those with cisplatin, doxorubicin, 5-fluorouracil and 5 x 3 Gray and comparable with cyclophosphamide and gemcitabine. Combination studies were carried out in human tumor xenografts including the MX-1 breast carcinoma, the Calu-6 non-small cell lung carcinoma, the H82 small cell lung carcinoma and the SW-2 small cell lung carcinoma. CRYPTO 52 and CRYPTO 55 combined with doxorubicin, paclitaxel and 5-fluorouracil to form highly effective regimens against the human MX-1 breast carcinoma. CRYPTO 52 and CRYPTO 55 were also highly effective against the three lung carcinoma xenografts when combined with the antitumor platinum complexes, cisplatin, carboplatin or oxaliplatin.

CONCLUSIONS

Cryptophycins represent a promising new class of antitumor agents that may be optimally administered by intravenous infusion and in combination with doxorubicin, paclitaxel and 5-fluorouracil.

A high-performance liquid chromatography method using ultraviolet and fluorescence detection for the quantitation of UCN-01, 7-hydroxystaurosporine, from human plasma and saliva

UCN-01, 7-hydroxystaurosporine, is an antagonist of protein kinase C, as well as causing cell cycle arrest. We developed and validated an HPLC assay method for the quantitation of UCN-01. Plasma and saliva standard curves were prepared at concentrations ranging from 0.2 to 20.0 microgram/mL and 4.0 to 200.0 ng/mL, respectively. The sample preparation consisted of acetonitrile precipitation. Separation was accomplished on a phenyl column and a C-18 precolumn insert utilizing a gradient-profile consisting of ammonium acetate and acetonitrile. UV detection was set at 295 nm for UCN-01 and 323 nm for umbelliferone, the internal standard. For fluorescence detection, excitation occurred at 290 nm, while emission was at 400 nm. The retention times were around 4 min for umbelliferone and 9.1 for UCN-01. Inter- and intra-assay errors of accuracy were less than 7. 0% and 10.7%, respectively, for the plasma standard curve and less than 7.1% and 6.7%, respectively, for the saliva standard curve. The recoveries of UCN-01 and umbelliferone from saliva were 81.4 +/- 0. 9% and 106.3 +/- 10.2%, respectively. The recovery of UCN-01 from plasma was 97.9 +/- 7.1% and for umbelliferone was 103.3 +/- 2.3%. This method is suitable for quantifying UCN-01 in patient samples and further characterizing the clinical pharmacology of this compound. Published in 2000 by John Wiley & Sons, Ltd.

Cryptophycin 52 and cryptophycin 55 in sequential and simultaneous combination treatment regimens in human tumor xenografts

The antitumor activity of cryptophycin 52 (C52) and cryptophycin 55 (C55) in sequential and simultaneous combination treatment regimens in human tumor xenografts models was explored. The antitumor activity of C52 and C55 was compared alone and in sequential combination with gemcitabine or paclitaxel in four lung cancer models, H460 and Calu-6 NSCLC and SW2 and H82 small cell lung carcinoma. The combination of C52 followed by gemcitabine was additive in three tumors and greater-than-additive in the fourth. The combination of C55 followed by gemcitabine was additive in three tumors and less-than-additive in the fourth. The combination of C52 followed by paclitaxel was greater-than-additive in one tumor, additive in one tumor and less-than-additive in two tumors. The combination of C55 followed by paclitaxel was greater-than-additive in two tumors and less-than-additive in two tumors. The simultaneous combination of C52 or C55 with fractionated radiation therapy was assessed in the H460 NSCLC tumor. Both cryptophycins produced a tumor response that was additive along with radiation therapy. The HCT116 colon carcinoma was used to compare the antitumor activity of simultaneous or sequential combination of 5-fluorouracil or irinotecan with C52. C52 produced greater-than-additive tumor response when administered either simultaneously with or sequentially with 5-fluorouracil or iriniotecan. Finally, when administered to animals bearing intraperitoneal OVCAR-3 ovarian carcinoma, C52, docetaxel and paclitaxel resulted in mean survival times of 123, 80 and 85 days compared with 72 days in the untreated controls. In combination with carboplatin, C52, docetaxel and paclitaxel resulted in mean survival times of 140, 105 and 135 days. Cryptophycins have the potential to be useful chemotherapeutic agents in a wide variety of clinical combinations regimens.

A frequent, naturally occurring mutation (P130T) of human hepatitis B virus core antigen is compensatory for immature secretion phenotype of another frequent variant (I97L)

A frequent mutation at codon 97 of human hepatitis B virus core antigen has been shown to cause an "immature secretion" phenotype, featuring nonselective and excessive secretions of virions containing immature viral genome. Our current study demonstrates that this abnormality can be efficiently offset by another frequent core mutation, P130T.

Treatment regimens including the multitargeted antifolate LY231514 in human tumor xenografts

The scheduling of antifolate antitumor agents, including the new multitargeted autofolate LY231514 (MTA), with 5-fluorouracil was explored in the human MX-1 breast carcinoma and human H460 and Calu-6 non-small cell lung carcinoma xenografts to assess antitumor activity and toxicity (body weight loss). Administration of the antifolate (methotrexate, MTA, or LY309887) 6 h prior to administration of 5-fluorouracil resulted in additive growth delay of the MX-1 tumor when the antifolate was methotrexate or LY309887 and greater-than-additive tumor growth delay (TGD) when the antifolate was MTA. In the H460 tumor, the most effective regimens were a 14-day course of MTA or LY309887 along with 5-fluorouracil administered on the final 5 days. In addition, the simultaneous combination of MTA administered daily for 5 days for 2 weeks with administration of gemcitabine resulted in greater-than-additive H460 TGD. MTA was additive with fractionated radiation therapy in the H460 tumor when the drug was administered prior to each radiation fraction. MTA administered along with paclitaxel produced greater-than-additive H460 TGD and additive responses along with vinorelbine and carboplatin. In the Calu-6 non-small cell lung carcinoma xenograft, MTA administered in combination with cisplatin or oxaliplatin was highly effective, whereas MTA administered in combination with cyclophosphamide, gemcitabine, or doxorubicin produced additive responses. Administration of MTA along with paclitaxel or doxorubicin resulted in additive MX-1 TGD. Thus, MTA appears to be especially effective in combination therapies including 5-fluorouracil or an antitumor platinum complex.

Suprasegmental and segmental timing models in Mandarin Chinese and American English

This paper formalizes and tests two key assumptions of the concept of suprasegmental timing: segmental independence and suprasegmental mediation. Segmental independence holds that the duration of a suprasegmental unit such as a syllable or foot is only minimally dependent on its segments. Suprasegmental mediation states that the duration of a segment is determined by the duration of its suprasegmental unit and its identity, but not directly by the specific prosodic context responsible for suprasegmental unit duration. Both assumptions are made by various versions of the isochrony hypothesis [I. Lehiste, J. Phonetics 5, 253-263 (1977)], and by the syllable timing hypothesis [W. Campbell, Speech Commun. 9, 57-62 (1990)]. The validity of these assumptions was studied using the syllable as suprasegmental unit in American English and Mandarin Chinese. To avoid unnatural timing patterns that might be induced when reading carrier phrase material, meaningful, nonrepetitive sentences were used with a wide range of lengths. Segmental independence was tested by measuring how the average duration of a syllable in a fixed prosodic context depends on its segmental composition. A strong association was found; in many cases the increase in average syllabic duration when one segment was substituted for another (e.g., bin versus pin) was the same as the difference in average duration between the two segments (i.e., [b] versus [p]). Thus, the [i] and [n] were not compressed to make room for the longer [p], which is inconsistent with segmental independence. Syllabic mediation was tested by measuring which locations in a syllable are most strongly affected by various contextual factors, including phrasal position, within-word position, tone, and lexical stress. Systematic differences were found between these factors in terms of the intrasyllabic locus of maximal effect. These and earlier results obtained by van Son and van Santen [R. J. J. H van Son and J. P. H. van Santen, "Modeling the interaction between factors affecting consonant duration," Proceedings Eurospeech-97, 1997, pp. 319-322] showing a three-way interaction between consonantal identity (coronals vs labials), within-word position of the syllable, and stress of surrounding vowels, imply that segmental duration cannot be predicted by compressing or elongating segments to fit into a predetermined syllabic time interval. In conclusion, while there is little doubt that suprasegmental units play important predictive and explanatory roles as phonological units, the concept of suprasegmental timing is less promising.

A pigment-binding protein essential for regulation of photosynthetic light harvesting

Photosynthetic light harvesting in plants is regulated in response to changes in incident light intensity. Absorption of light that exceeds a plant's capacity for fixation of CO2 results in thermal dissipation of excitation energy in the pigment antenna of photosystem II by a poorly understood mechanism. This regulatory process, termed nonphotochemical quenching, maintains the balance between dissipation and utilization of light energy to minimize generation of oxidizing molecules, thereby protecting the plant against photo-oxidative damage. To identify specific proteins that are involved in nonphotochemical quenching, we have isolated mutants of Arabidopsis thaliana that cannot dissipate excess absorbed light energy. Here we show that the gene encoding PsbS, an intrinsic chlorophyll-binding protein of photosystem II, is necessary for nonphotochemical quenching but not for efficient light harvesting and photosynthesis. These results indicate that PsbS may be the site for nonphotochemical quenching, a finding that has implications for the functional evolution of pigment-binding proteins.

Subtype-independent immature secretion and subtype-dependent replication deficiency of a highly frequent, naturally occurring mutation of human hepatitis B virus core antigen

The most frequent mutation of the human hepatitis B virus (HBV) core antigen occurs at amino acid 97. Recently, a phenylalanine (F)-to-leucine (L) mutation at this position (mutant F97L) in HBV surface antigen subtype ayw has been shown to result in an immature secretion phenotype, which is characterized by the nonselective export of an excessive amount of virions containing minus-strand, single-stranded HBV DNA. While subtype ayw mutant F97L has been found in Europe, the major reservoir of HBV resides in Asia and Africa. We report here that the immature secretion phenotype indeed can be found in an HBV strain (subtype adr) prevalent in Asia, changing from an isoleucine (I) to a leucine (mutant I97L). Despite its immature secretion phenotype, the adr variant I97L replicates as well as its parental adr wild-type I97I, supporting the conclusion that the extracellular phenotype of immature secretion is not a consequence of the intracellular HBV DNA replication defect. Further studies demonstrated that it is the acquisition of a leucine, rather than the loss of a wild-type amino acid at codon 97, that is important for immature secretion. We conclude that immature secretion is a subtype-independent phenotype and deficiency in intracellular DNA synthesis is a subtype-dependent phenotype. The former is caused by the trans-acting effect of a mutant core protein, while the latter by a cis-acting effect of a mutated nucleotide on the ayw genome. These immature secretion variants provide an important tool for studying the regulation of HBV virion assembly and secretion.