C-Arm Computed Tomographic Image Fusion for Repetitive Transarterial Chemoembolization of Hepatocellular Carcinoma

OBJECTIVE

The aim of this study was to evaluate the potential implications of fusion imaging with C-arm computed tomography (CACT) scans for repetitive conventional transarterial chemoembolization (cTACE) for hepatocellular carcinoma.

MATERIALS AND METHODS

Fifty-six cTACE sessions were performed using fusion CACT images from September 2020 to June 2021 in a tertiary referral center, and the data were retrospectively analyzed. Fusion of unenhanced and enhanced CACT images was considered when previously accumulated iodized oil hampered the identification of local tumor progression or intrahepatic distant metastasis (indication A), when a tumor was supplied by multiple arteries with different origins from the aorta and missing tumor enhancement was suspected (indication B), or when iodized oil distribution on immediate post-cTACE CACT images needed to be precisely compared with the pre-cTACE images (indication C). Fusion image quality, initial tumor response, time to local progression (TTLP) of index tumors, and time to progression (TTP) were evaluated.

RESULTS

The fusion quality was satisfactory with a mean misregistration distance of 1.4 mm. For the 40 patients with indication A, the initial tumor responses at 3 months were nonviable, equivocal, and viable in 27 (67.5%), 4 (10.0%), and 9 (22.5%) index tumors, respectively. The median TTLP and TTP were 14.8 months and 4.5 months, respectively. For 10 patients with indication B, the median TTLP and TTP were 8.3 months and 2.6 months, respectively. Among the 6 patients with indication C, 2 patients were additionally treated at the same cTACE session after confirming incomplete iodized oil uptake on fusion imaging.

CONCLUSIONS

Fusion CACT images are useful in patients with hepatocellular carcinoma undergoing repetitive cTACE.

The spectrum of imaging manifestations of Gorham-Stout disease: a novel dynamic contrast-enhanced MR lymphangiography

BACKGROUND

To describe the radiological features of Gorham-Stout disease (GSD) as evaluated using plain radiography and dynamic contrast-enhanced magnetic resonance lymphangiography (DCMRL) imaging techniques.

METHODS

Clinical and conventional imaging data were retrospectively reviewed for 15 patients with GSD between January 2001 and December 2020. After December 2018, DCMRL examinations were performed for lymphatic vessel evaluation in patients with GSD and reviewed in four patients.

RESULTS

The median age at diagnosis was 9 years (range: 2 months-53 years). The clinical manifestations were dyspnea in seven patients (46.7%), sepsis in 12 (80.0%), orthopedic problems in seven (46.7%), and bloody chylothorax in seven (46.7%). The common sites of osseous involvement were the spine (73.3%) and pelvic bone (60.0%). Among the non-osseous involvements, peri-osseous infiltrative soft-tissue abnormalities adjacent to the area of bone involvement were the most common (86.7%), followed by splenic cysts (26.7%) and interstitial thickening (26.7%). DCMRL demonstrated weak central conducting lymphatic flow in two patients with abnormal giant tortuous thoracic ducts and no flow in one patient. All patients who underwent DCMRL in this study presented with altered anatomical lymphatics and functional flow with collateralization.

CONCLUSION

DCMRL imaging and plain radiography are very useful for determining the extent of GSD. DCMRL is a novel imaging tool for the visualization of abnormal lymphatics in patients with GSD, which helps in further treatment. Therefore, in patients with GSD, it might be necessary to obtain not only plain radiographs but also MR and DCMRL images.

Transcatheter arterial embolization of cystic artery bleeding

Purpose

The purpose of this study is to assess the safety and clinical outcomes of transcatheter arterial embolization (TAE) via the cystic artery for treating patients with bleeding from the cystic artery.

Materials and Methods

This retrospective study included 20 patients who underwent TAE via the cystic artery between January 2010 and May 2022. Radiological images and clinical data were reviewed to evaluate causes of bleeding, procedure-related complications, and clinical outcomes. Technical success was defined as the disappearance of contrast media extravasation or pseudoaneurysm, as demonstrated on completion angiography. Clinical success was defined as discharge from the hospital without any bleeding-related issues.

Results

Hemorrhagic cholecystitis (n = 10) was the most common cause of bleeding, followed by iatrogenic (n = 4), duodenal ulcer (n = 3), tumor (n = 2), and trauma (n = 1). Technical success was achieved in all cases, and clinical success was achieved in 70% (n = 14) of patients. Three patients developed ischemic cholecystitis as a complication. Six patients with clinical failure died within 45 days after embolization.

Conclusion

TAE through the cystic artery has a high technical success rate in treating cystic artery bleeding, but clinical failure remains a common occurrence due to concurrent medical conditions and the development of ischemic cholecystitis.

Clinical course and role of embolization in patients with spontaneous rupture of hepatocellular carcinoma

Background

A diverse clinical course after the spontaneous rupture of hepatocellular carcinoma (HCC) renders nonstandardized treatment protocols.

Purpose

To evaluate clinical course and role of transcatheter arterial embolization (TAE) in patients with rupture of HCC.

Materials and methods

This retrospective study included 127 patients who were treated for ruptured HCC at single institution between 2005 and 2014. After multidisciplinary discussion, patients underwent medical management, TAE, emergency surgery or staged surgery. Patients were retrospectively divided into two groups based on the intent of treatment: curative and palliative. The rebleeding rate and 1-month and overall survival (OS) were compared between two groups. The incidence and survival of patients with intraperitoneal drop metastasis (IPDM) were also analyzed.

Results

The overall rebleeding rate in patients who underwent TAE was 3.1% (3/96). One-month mortality rate was 6.3% (8/127). The rebleeding and 1-month mortality rates were not significantly different between two groups. OS was significantly higher in the curative treatment group (median: 12.0 vs 2.2 months, p<0.001). Among 96 patients who initially received TAE, ten patients underwent staged operation (10.4%). The median OS for medical management, TAE, emergency surgery and staged surgery was 2.8, 8.7, 19.1 and 71.1 months, respectively. Of all patients, 15.2% developed IPDM mostly within 1 year and their survival was poorer than that of patients without IPDM (median: 6.3 vs. 15.1 months, p<0.001).

Conclusion

TAE provided effective immediate hemostasis with a low rebleeding rate and may serve as a bridge to elective surgery. IPDM frequently occurred within 1 year and manifested poor survival; thus, close surveillance should be considered for patients with spontaneous rupture of HCC.

Thoracic duct embolization in treating postoperative chylothorax: does bail-out retrograde access improve outcomes?

OBJECTIVES

To evaluate clinical outcomes of thoracic duct embolization (TDE) for the management of postoperative chylothorax with the aid of the bail-out retrograde approach for thoracic duct cannulation (TDC).

MATERIALS AND METHODS

Forty-five patients with postoperative chylothorax underwent Lipiodol lymphangiography (LLG) between February 2016 and November 2019. If targetable central lymphatic vessels were identified in LLG, TDC, a prerequisite for TDE, was attempted. While the conventional antegrade transabdominal approach was the standard TDC method, the retrograde approach was applied as a bail-out method. Embolization, the last step of TDE, was performed after confirming leakages in the trans-TDC catheter lymphangiography. Technical and clinical success rates were determined retrospectively.

RESULTS

TDC was attempted in 40 among 45 patients based on LLG findings. The technical success rate of TDC with the conventional antegrade approach was 78% (31/40). In addition, six more patients were cannulated using the bail-out retrograde approach, which raised the technical success rate to 93% (37/40). While 35 patients underwent embolization (TDE group), ten patients did not (non-TDE group) for the following reasons: (1) lack of targetable lymphatics for TDC in LLG (n = 5), (2) technical failure of TDC (n = 3), and (3) lack of discernible leakages in the transcatheter lymphangiography (n = 2). The clinical success of the TDE group was 89% (31/35), compared with 50% (5/10) of the non-TDE group. One major procedure-related complication was bile peritonitis caused by the needle passage of the distended gallbladder.

CONCLUSIONS

Bail-out retrograde approach for TDC could improve the overall technical success of TDC significantly.

KEY POINTS

• Bail-out retrograde thoracic duct access may improve the overall technical success of thoracic duct access, thus improving the clinical success of thoracic duct embolization.

New metformin derivative HL156A prevents oral cancer progression by inhibiting the insulin-like growth factor/AKT/mammalian target of rapamycin pathways

Metformin is a biguanide widely prescribed as an antidiabetic drug for type 2 diabetes mellitus patients. The purpose of the present study was to observe the effects of the new metformin derivative, HL156A, on human oral cancer cell and to investigate its possible mechanisms. It was observed that HL156A significantly decreased FaDu and YD‐10B cell viability and colony formation in a dose‐dependent way. HL156A also markedly reduced wound closure and migration of FaDu and YD‐10B cells. We observed that HL156A decreased mitochondrial membrane potential and induced reactive oxygen species (ROS) levels and apoptotic cells with caspase‐3 and ‐9 activation. HL156A inhibited the expression and activation of insulin‐like growth factor (IGF)‐1 and its downstream proteins, AKT, mammalian target of rapamycin (mTOR), and ERK1/2. In addition, HL156A activated AMP‐activated protein kinase/nuclear factor kappa B (AMPK‐NF‐κB) signaling of FaDu and YD‐10B cells. A xenograft mouse model further showed that HL156A suppressed AT84 mouse oral tumor growth, accompanied by down‐regulated p‐IGF‐1, p‐mTOR, proliferating cell nuclear antigen (PCNA) and promoted p‐AMPK and TUNEL expression. These results suggest the potential value of the new metformin derivative HL156A as a candidate for a therapeutic modality for the treatment of oral cancer.

Characterization of DDRI-18 (3,3'-(1H,3'H-5,5'-bibenzo[d]imidazole-2,2'-diyl)dianiline), a novel small molecule inhibitor modulating the DNA damage response

BACKGROUND AND PURPOSE

Recently, the DNA damage response (DDR) has emerged as a promising target for anticancer drug development. In our previous study, we identified several DDR-inhibiting compounds via high-content screening of a small molecule library using γH2AX foci as a biomarker. Here, we studied the effects of the DNA damage response inhibitor DDRI-18 (3,3'-(1H,3'H-5,5'-bibenzo[d]imidazole-2,2'-diyl)dianiline) on DDR.

EXPERIMENTAL APPROACH

Osteosarcoma U2OS cells were treated with etoposide to induce DDR. The nuclear foci of γH2AX and other signalling molecules in DDR were visualized by immunofluorescence and quantified using an IN Cell Analyzer. The DNA repair capacity of cells was analysed using the comet assay and in vivo DNA end-joining assay. Cell survival after drug treatment was quantified using the MTT assay, and apoptotic cell death was analysed by Annexin V staining and flow cytometry.

KEY RESULTS

DDRI-18 inhibited the non-homologous end-joining (NHEJ) DNA repair process and delayed the resolution of DNA damage-related proteins (γH2AX, ATM and BRCA1) from DNA lesions at a later phase of DDR. Furthermore, DDRI-18 enhanced the cytotoxic effects of anticancer DNA-damaging drugs, including etoposide, camptothecin, doxorubicin and bleomycin. This synergistic effect on cell death was shown to be due to caspase-dependent apoptosis.

CONCLUSIONS AND IMPLICATIONS

We identified a chemical compound, DDRI-18, that has chemosensitization activity. Although the target molecule and mechanism of action of DDRI-18 remain unknown, DDRI-18 is an effective chemosensitizing agent and may improve the therapy with classical anticancer drugs.

Highly polarization-dependent periodic coupling in mechanically induced long period grating over air-silica fibers

A very flexible and versatile tunable mechanical grating platform is introduced, with which highly polarization-dependent mode coupling is observed for three types of air-silica microstructured fibers: hollow core fiber, hexagonal-boundary holey fiber (HHF), and circular-boundary holey fiber. The resonances of gratings showed highly polarization-dependent broadband coupling compared with conventional single-mode fibers due to their unique beat-length dispersions between the core and the cladding modes, which could find applications in wideband polarization-dependent loss compensation. We further present significance of the spatial symmetry of HHF in distinct mode coupling for different rotation angles around the fiber axis.

Targeted Degradation of Proteins by Small Molecules: A Novel Tool for Functional Proteomics†

A novel strategy that targets protein for degradation has recently been developed by exploiting a protein-targeting chimeric molecule ('Protac'). Typically, the chimeric Protac is composed of a small-molecule ligand ('bait') on one end and a synthetic octapeptide on the other. This octapeptide is recognized by E3 ubiquitin ligase pVHL (von Hippel Lindau tumor suppressor protein), thereby recruiting a small molecule-bound protein ('prey') to pVHL for ubiquitination and degradation. Since selective degradation of a cellular protein generates a "loss of function" mutation, this protein knock-out strategy may be useful to study the function of a given protein or to evaluate whether a cellular protein is a potential target for drug intervention, in a manner reminiscent of gene knock-out or siRNA approaches. Herein, we show that a synthetic pentapeptide is sufficient to interact with pVHL E3 ligase, and that the pentapeptide-based Protac efficiently induces ubiquitination and degradation of target protein. Our results also demonstrate that the pentapeptide-based Protac can enter cells efficiently to exerts its biological activity effectively. These results suggest that the synthetic pentapeptide can be used either directly in the preparation of cell-permeable Protacs or as a template to develop peptidomimetic or non-peptide Protacs.

A new guaiane type sesquiterpene from Torilis japonica

A new guaiane type sesquiterpene was isolated from the fruit of Torilis japonica (Umbelliferae). Based on NMR, IR and mass spectroscopy its structure was confirmed as deangeloyloxy torilin, 1beta, 7alpha, 10alphaH-11-acetoxy-guaia-4-en-3-one (1). This is the first report showing that this compound can be isolated from Torilis japonica.

Short report: genetic heterogeneity of Japanese encephalitis virus assessed via analysis of the full-length genome sequence of a Korean isolate

We determined the full-length genome sequence of Japanese encephalitis virus (JEV) K94P05 isolated in Korea. Sequence analysis showed that the 10,963-nucleotide-long RNA genome of K94P05 was 13 or 14 nucleotides shorter than the genome of other JEV isolates because of a deletion in the 3' noncoding region of K94P05. Compared with sequences of other JEV isolates, the full-length nucleotide sequence showed 89.0-89.6% homology, and the deduced amino acid sequence showed between 96.4-97.3% homology. A region of approximately 60 nucleotides immediately downstream of the open reading frame stop codon of K94P05 showed high sequence variability as compared with other JEV isolates. K94P05 formed a distinct group within a phylogenetic tree established with the full-length genome sequences. Cross-neutralization studies showed that polyclonal antibodies to Korean isolates were 3 times better at neutralizing the Korean isolates than antibodies to Nakayama-NIH. These findings suggest that Korean JEV K94P05 is genetically and antigenically distinct from other Asian JEV isolates.

Risk factors for infection and role of C-reactive protein in Korean patients with systemic lupus erythematosus

To evaluate risk factors for infection and the role of C-reactive protein (CRP) in the diagnosis of infection, a retrospective case control study was performed among Korean systemic lupus erythematosus patients. Of 120 proven infections, 31 episodes (25.8%) occurred in patients taking no corticosteroids (CS). The risk of infection was lower in patients taking low-dose CS (< 300 mg prednisolone/month) than no CS (odds ratio (OR) 0.36). In patients receiving high-dose CS (> 1000 mg prednisolone/month), however, the risk increased (OR 2.9). In patients taking no CS, disease activity manifested as increased SLEDAI, anemia and active urinary sediment, was associated with infection. The CRP was higher in the patients with infection than controls and the CRP levels over 50 mg/l were observed only in infection. These results suggest that CS have a bimodal influence on infection depending on dose. Disease activity is an important risk factor for infection in patients taking no CS. Finally, CRP levels greater than 50 mg/l suggest the presence of infection.

Comparison of the efficacy and safety of different formulations of omeprazole-based triple therapies in the treatment of Helicobacter pylori-positive peptic ulcer

Little is known about the efficacy and safety of different formulations of omeprazole-based triple therapy regimens for the treatment of Helicobacter pylori-positive peptic ulcer. We compared the efficacy and safety of two formulations of omeprazole used in triple therapies in patients with H. pylori-positive active peptic ulcer. Seventy-four patients with endoscopically proven H. pylori-positive active peptic ulcer were randomized to two groups, each with 37 patients, to receive either OAC-I (6 weeks of "A" formulation of omeprazole [20 mg twice daily] plus 2 weeks of amoxicillin [1.0 g twice daily] and clarithromycin [500 mg twice daily] or OAC-II (6 weeks of "B" formulation of omeprazole [20 mg twice daily] plus 2 weeks of the same antibiotics. The H. pylori and ulcer healing status were assessed at the baseline and at the 6-week endpoint of therapy. Gastrointestinal symptoms, documentation of adverse events, and standard laboratory examinations were assessed at each visit. Eradication of H. pylori (intention to treat [n = 74]/per protocol [n = 66]) and healing of the ulcer were successful in 83.8%/96.9% and 93.8%, respectively, of the OAC-I group patients, and in 91.9%/100% and 97.1%, respectively, of the OAC-II group patients (P = 0.477; P = 0.608). The OAC-I group experienced rapid resolution of symptoms, but no significant differences were found between the two groups for number of days taken for resolution of gastrointestinal symptoms, adverse events, and laboratory findings. The two different formulations of omeprazole used in triple therapy regimens produced similar efficacy and safety results after 6 weeks of treatment in patients with H. pylori-positive active peptic ulcer.

Bioconversion of cellulose into ethanol by nonisothermal simultaneous saccharification and fermentation

The kinetic characteristics of cellulase and beta-glucosidase during hydrolysis were determined. The kinetic parameters were found to reproduce experimental data satisfactorily and could be used in a simultaneous saccharification and fermentation (SSF) system by coupling with a fermentation model. The effects of temperature on yeast growth and ethanol production were investigated in batch cultures. In the range of 35-45 degrees C, using a mathematical model and a computer simulation package, the kinetic parameters at each temperature were estimated. The appropriate forms of the model equation for the SSF considering the effects of temperature were developed, and the temperature profile for maximizing the ethanol production was also obtained. Briefly, the optimum temperature profile began at a low temperature of 35 degrees C, which allows the propagation of cells. Up to 10 h, the operating temperature increased rapidly to 39 degrees C, and then decreased slowly to 36 degrees C. In this nonisothermal SSF system with the above temperature profile, a maximum ethanol production of 14.87 g/L was obtained.

Successful treatment of protein-losing enteropathy due to AA amyloidosis with somatostatin analogue and high dose steroid in ankylosing spondylitis

Secondary amyloidosis is an occasional complication of ankylosing spondylitis (AS) and in most cases renal amyloidosis presents with proteinuria, nephrotic syndrome and decreased renal function. We describe a 32-year-old male patient with AS manifested by frequent diarrhea, intermittent abdominal pain and low serum albumin levels. He has suffered from severe inflammatory back pain for 14 years with multiple peripheral joint involvement. Protein-losing enteropathy due to gastrointestinal amyloidosis was diagnosed with 99mTc-human albumin scintigraphy, fecal alpha-1 antitrypsin clearance and colonoscopic biopsy with Congo red staining. Somatostatin analogue octreotide and prednisolone were introduced with successful result.

A new bisabolene epoxide from Tussilago farfara, and inhibition of nitric oxide synthesis in LPS-activated macrophages

A new bisabolene epoxide was isolated from the flower buds of Tussilago farfara, and the structure was determined by spectroscopic methods to be 1alpha,5alpha-bisacetoxy-8-angeloyloxy-3beta, 4beta-epoxy-bisabola-7(14),10-dien-2-one (1). Compound 1 showed inhibition of nitric oxide synthesis in lipopolysaccharide-activated macrophages.

Yomogin, an inhibitor of nitric oxide production in LPS-activated macrophages

In activated macrophages the inducible form of nitric oxide synthase (i-NOS) generates high amounts of toxic mediator, nitric oxide (NO) which contributes to the circulatory failure associated with septic shock. A sesquiterpene lactone compound (yomogin) isolated from medicinal plant Artemisia princeps Pampan inhibited the production of NO in LPS-activated RAW 264.7 cells by suppressing i-NOS enzyme expression. Thus, yomogin may be a useful candidate for the development of new drugs to treat endotoxemia and inflammation accompanied by the overproduction of NO.

Coronavirus transcription mediated by sequences flanking the transcription consensus sequence

In our studies of murine coronavirus transcription, we continue to use defective interfering (DI) RNAs of mouse hepatitis virus (MHV) in which we insert a transcription consensus sequence in order to mimic subgenomic RNA synthesis from the nondefective genome. Using our subgenomic DI system, we have studied the effects of sequences flanking the MHV transcription consensus sequence on subgenomic RNA transcription. We obtained the following results. (i) Insertion of a 12-nucleotide-long sequence including the UCUAAAC transcription consensus sequence at different locations of the DI RNA resulted in different efficiencies of subgenomic DI RNA synthesis. (ii) Differences in the amount of subgenomic DI RNA were defined by the sequences that flanked the 12-nucleotide-long sequence and were not affected by the location of the 12-nucleotide-long sequence on the DI RNA. (iii) Naturally occurring flanking sequences of intergenic sequences at gene 6-7, but not at genes 1-2 and 2-3, contained a transcription suppressive element(s). (iv) Each of three naturally occurring flanking sequences of an MHV genomic cryptic transcription consensus sequence from MHV gene 1 also contained a transcription suppressive element(s). These data showed that sequences flanking the transcription consensus sequence affected MHV transcription.

Pathogenicity of live, attenuated SIV after mucosal infection of neonatal macaques

Adult macaques do not develop disease after infection with a nef deletion mutant of the simian immunodeficiency virus (SIV) and are protected against challenge with pathogenic virus. This finding led to the proposal to use nef-deleted viruses as live, attenuated vaccines to prevent human acquired immunodeficiency syndrome (AIDS). In contrast, neonatal macaques developed persistently high levels of viremia after oral exposure to and SIV nef, vpr, and negative regulatory element (NRE) deletion mutant. Severe hemolytic anemia, thrombocytopenia, and CD4+ T cell depletion were observed, indicating that neither nef nor vpr determine pathogenicity in neonates. Because such constructs have retained their pathogenic potential, they should not be used as candidate live, attenuated virus vaccines against human AIDS.

Evidence for coronavirus discontinuous transcription

Coronavirus subgenomic mRNA possesses a 5'-end leader sequence which is derived from the 5' end of genomic RNA and is linked to the mRNA body sequence. This study examined whether coronavirus transcription involves a discontinuous transcription step; the possibility that a leader sequence from mouse hepatitis virus (MHV) genomic RNA could be used for MHV subgenomic defective interfering (DI) RNA transcription was examined. This was tested by using helper viruses and DI RNAs that were easily distinguishable. MHV JHM variant JHM(2), which synthesizes a subgenomic mRNA encoding the HE gene, and variant JHM(3-9), which does not synthesize this mRNA, were used. An MHV DI RNA, DI(J3-9), was constructed to contain a JHM(3-9)-derived leader sequence and an inserted intergenic region derived from the region preceding the MHV JHM HE gene. DI(J3-9) replicated efficiently in JHM(2)- or JHM(3-9)-infected cells, whereas synthesis of subgenomic DI RNAs was observed only in JHM(2)-infected cells. Sequence analyses demonstrated that the 5' regions of both helper virus genomic RNAs and genomic DI RNAs maintained their original sequences in DI RNA-replicating cells, indicating that the genomic leader sequences derived from JHM(2) functioned for subgenomic DI RNA transcription. Replication and transcription of DI(J3-9) were observed in cells infected with an MHV A59 strain whose leader sequence was similar to that of JHM(2), except for one nucleotide substitution within the leader sequence. The 5' region of the helper virus genomic RNA and that of the DI RNA were the same as their original structures in virus-infected cells, and the leader sequence of DI(J3-9) subgenomic DI RNA contained the MHV A59-derived leader sequence. The leader sequence of subgenomic DI RNA was derived from that of helper virus; therefore, the genomic leader sequence had a trans-acting property indicative of a discontinuous step in coronavirus transcription.

Analysis of cis-acting sequences essential for coronavirus defective interfering RNA replication

Mouse hepatitis virus (MHV) defective interfering (DI) RNA was used to determine the cis-acting sequences required for MHV RNA replication. A 2.2-kb-long cDNA clone of the MHV DI RNA DIssE was used to test the effect of deletions throughout the DI RNA on replication in DI RNA-transfected, MHV-infected cells. Data from a series of deletion mutants demonstrated that about 470 nucleotides at the 5' terminus, 460 nucleotides at the 3' terminus, and about 135 nucleotides in an internal position approximately 0.9 kb from the 5' end of DI RNA were necessary for DI RNA replication. These data suggested that cis-acting sequences which were necessary for MHV RNA replication required not only terminal sequences but also an internal sequence present at about 3.2 kb from the 5' end of the genome.

Mechanism of coronavirus transcription: duration of primary transcription initiation activity and effects of subgenomic RNA transcription on RNA replication

Previously, we established a system whereby an intergenic region from mouse hepatitis virus (MHV) inserted into an MHV defective interfering (DI) RNA led to transcription of a subgenomic DI RNA in helper virus-infected cells. By using this system, the duration of a primary transcription initiation activity which transcribes subgenomic-size RNAs from the genomic-size RNA template in MHV-infected cells was examined. Efficient DI genomic and subgenomic RNA synthesis was observed when the DI RNA was transfected at 1, 3, 3.5, 5, and 6 h postinfection, indicating that all activities which are necessary for MHV RNA synthesis are present continuously during the first 6 h of infection. The effect of subgenomic DI RNA synthesis on DI genomic RNA replication was then examined. Replication efficiency of the DI genomic RNA which synthesized the subgenomic RNA was approximately 70% lower than that of DI genomic RNA which did not synthesize the subgenomic DI RNA in MHV-infected cells. Cotransfection of two different-size DI RNAs demonstrated that replication of the larger DI RNA was strongly inhibited by replication of the smaller genomic DI RNA. Cotransfection of two DI RNA species of the same length into MHV-infected cells demonstrated that reduced replication of the genomic DI RNA which synthesizes the subgenomic RNA did not affect the replication of cotransfected DI RNA, demonstrating that the reduction in DI genomic RNA replication works only in cis, not in trans. Therefore, the previously proposed hypothesis that coronavirus, subgenomic RNA synthesis may inhibit the replication of genomic RNA by competing for a limited amount of virus-derived factors seems unlikely. Possible mechanisms of coronavirus transcription are discussed.

Transport and kinetics in sandwiched membrane bioreactors

A bioreactor in which living yeast cells are sandwiched between an ultrafiltration membrane and a reverse osmosis membrane was constructed, and experiments were performed for the conversion of substrate glucose to product ethanol. A set of equations that include both transport through a series of barrier layers and bioreaction rate were developed to predict the performance of the sandwich bioreactor. The above equations were solved by using numerical values for the transport parameter and the bioreaction rate constant, and the results are compared with the experimental data.