Clinical predictors of polyps recurring in patients with chronic rhinosinusitis and nasal polyps: a systematic review and meta-analysis

BACKGROUND

Identification of perioperative risk factors for recurrent nasal polyps (RNPs) is important for selection of further treatment and determination of appropriate follow-up period. However, the relative prognostic significance of these risk factors has not been investigated.

METHODOLOGY

We compared the nasal symptoms, endoscopic polyp and Lund-Mackey computed tomography scores, and the laboratory and pathological findings of RNP and non-RNP patients. The risk of bias was assessed using the Newcastle-Ottawa scale.

RESULTS

Patients with poor nasal symptom scores and olfactory dysfunctions and high Lund-Mackey computed tomography scores were at higher risk of postoperative RNPs, as were those with allergic conditions and elevated tissue and serum eosinophil levels. The tissue neutrophil counts/percentages were significantly lower in the RNP than the other group. The tissue eosinophil level was of higher diagnostic utility than the serum eosinophil level. The RNP diagnostic odds ratio afforded by the tissue eosinophil count or percentage was 54.1247. The area under the receiver operating characteristic curve was 0.936. The sensitivity and specificity were 0.8809 and 0.8834, respectively.

CONCLUSION

The tissue eosinophil level reliably predicts RNP after endoscopic sinus surgery.

Lethal abdominal compartment syndrome after extracorporeal cardiopulmonary resuscitation in a patient with out-of-hospital cardiac arrest: a case report

BACKGROUND

Clinical attempts of extracorporeal cardiopulmonary resuscitation (ECPR) in patients with out-of-hospital cardiac arrest (OHCA) have increased in recent years; however, it also has life-threatening complications. Massive fluid and transfusion resuscitation, shock status, or low cardiac output status during ECPR may lead to ascites and interstitial edema, resulting in secondary abdominal compartment syndrome (ACS).

CASE PRESENTATION

A 43-year-old male patient was admitted to the emergency department due to cardiac arrest. Due to refractory ventricular fibrillation, ECPR was initiated. Approximately, 3 h after extracorporeal membrane oxygenation support, abdominal distension and rigidity developed. Therefore, ACS was suspected. Decompression laparotomy was required to relieve elevated intra-abdominal pressure.

CONCLUSIONS

We report a case of a patient with OHCA who developed lethal ACS after ECPR. Despite this, the patient was able to recover from several major crises. Regardless of how lethal the patient is, if compartment syndrome develops in any part of the body, we should aggressively consider surgical decompression.

Histone deacetylase inhibitor, mocetinostat, regulates cardiac remodelling and renin-angiotensin system activity in rats with transverse aortic constriction-induced pressure overload cardiac hypertrophy

Histone deacetylase (HDAC) inhibitors have shown cardioprotective or renoprotective effects in various animal models. Our study proposed that the HDAC inhibitor, mocetinostat, regulates cardiac remodelling and renin-angiotensin system (RAS) activity in rats with transverse aortic constriction (TAC)-induced pressure overload cardiac hypertrophy. Cardiac remodelling was evaluated using echocardiography. Cardiac hypertrophy was visualized with haematoxylin and eosin staining, and related gene (Nppa and Nppb) expression was quantified by quantitative real-time polymerase chain reaction (qRT-PCR). Cardiac and renal fibrosis were visualized with picrosirius red and trichrome staining, respectively. Fibrosis related gene (Collagen-1, Collagen-3, Ctgf, and Fibronectin) expression was determined by qRT-PCR. Serum concentrations of RAS components (renin, angiotensin II, and aldosterone) were quantified by enzyme-linked immunosorbent assay and related gene (Renin and Agtr1) expression was determined by qRT-PCR. TAC-induced pressure overload cardiac hypertrophy, which mimics hypertensive heart disease, increased cardiac remodelling, cardiac hypertrophy, and fibrosis in our rat models. Upon treatment with mocetinostat, there was a significant regression in cardiac remodelling, cardiac hypertrophy, and fibrosis in TAC rats. Additionally, pressure overload-induced renal fibrosis and activity of RAS-related components were increased in TAC rats, and were decreased on treatment with mocetinostat. The present study indicates that mocetinostat, an HDAC inhibitor, has cardiorenal protective effects in rats with TAC-induced pressure overload cardiac hypertrophy and offers a promising therapeutic agent for hypertension-related diseases.

Successful Management of a Rare Gastric Mucormycosis Presenting with Massive Melena in a Polytrauma Patient

Mucormycosis is a rare, life-threatening, and opportunistic fungal infection that usually occurs in immunocompromised patients. Rhinocerebral and pulmonary manifestations are the common form. The rare form of gastrointestinal mucormycosis occur in all parts of the alimentary tract, with emphasis on the stomach being the most common site. Primary gastric mucormycosis following traumatic injury is an extremely rare form that is usually lethal; thus, only a few cases of survival have been reported even after early diagnosis and aggressive surgical resection, combined with antifungal treatment. We herein report a case of delayed-onset gastric mucormycosis in a polytrauma patient without predisposing factors, which was successfully treated by antifungal medical therapy alone with no surgical debridement.

GW190521: A Binary Black Hole Merger with a Total Mass of 150 M_{⊙}

On May 21, 2019 at 03:02:29 UTC Advanced LIGO and Advanced Virgo observed a short duration gravitational-wave signal, GW190521, with a three-detector network signal-to-noise ratio of 14.7, and an estimated false-alarm rate of 1 in 4900 yr using a search sensitive to generic transients. If GW190521 is from a quasicircular binary inspiral, then the detected signal is consistent with the merger of two black holes with masses of 85_{-14}^{+21}  M_{⊙} and 66_{-18}^{+17}  M_{⊙} (90% credible intervals). We infer that the primary black hole mass lies within the gap produced by (pulsational) pair-instability supernova processes, with only a 0.32% probability of being below 65  M_{⊙}. We calculate the mass of the remnant to be 142_{-16}^{+28}  M_{⊙}, which can be considered an intermediate mass black hole (IMBH). The luminosity distance of the source is 5.3_{-2.6}^{+2.4}  Gpc, corresponding to a redshift of 0.82_{-0.34}^{+0.28}. The inferred rate of mergers similar to GW190521 is 0.13_{-0.11}^{+0.30}  Gpc^{-3} yr^{-1}.

Outcomes of open heart surgery in patients with end-stage renal disease

Background

Cardiovascular diseases of chronic dialysis patients are often undertreated because of their higher surgical risk. This study aimed to assess mortality and morbidity after open heart surgery in chronic dialysis patients compared to those with normal renal function and identify risk factors for postoperative outcomes.

Methods

We retrospectively analyzed 2,432 patients who underwent open heart surgery from 2002 to 2017 and collected data from 116 patients (38 patients on dialysis and 78 age-, sex-, and diabetes mellitus status-matched control patients with normal kidney function). We assessed comorbidities, New York Heart Association (NYHA) class, laboratory data, surgical methods, and postoperative outcomes.

Results

The dialysis group had more comorbidities, higher NYHA classes, and greater need for urgent surgeries compared to the control group. They exhibited significantly higher postoperative mortality (18.4% vs. 2.6%, P = 0.005) and more overall complications (65.8% vs. 25.6%, P < 0.001). Dialysis itself significantly increased relative risk for inhospital mortality after adjustment. EuroSCORE II was not as useful as in the general population. Multivariate logistic regression analysis demonstrated that total (adjusted odds ratio [AOR], 10.7; P = 0.029) and in-hospital death risk (AOR, 14.7; P = 0.033), the durations of postoperative hospitalization (AOR, 4.6; P = 0.034), CRRT (AOR 36.8; P = 0.004), and ventilator use (AOR, 7.6; P = 0.022) were significantly increased in the dialysis group.

Conclusion

The dialysis group exhibited a higher risk for mortality and overcall complications after open heart surgery compared to the patients with normal renal function. Therefore, the benefit of surgical treatment must be balanced against potential risks.

Thoracic aortic aneurysms exerting high extrinsic pressure on the airway

Background

Thoracic aortic aneurysms, although mostly asymptomatic, are life threatening owing to the risk of rupture. Moreover, the extrinsic pressure of a ruptured aneurysm may encroach the mediastinum.

Case presentation

A 74-year-old woman diagnosed with ruptured descending thoracic aortic aneurysm compressing the lower trachea and both main bronchi underwent thoracic endovascular aortic repair; however, the extrinsic pressure on the airway persisted. Following failing of endobronchial silicon stents insertion, extracorporeal membrane oxygenation support was required, and endobronchial metallic stents were inserted. The patients’ hypoventilation resolved, and the patient was withdrawn from the ventilator.

Conclusions

Technological improvement in endovascular or endobronchial procedures has provided more options for managing complex cases. However, we must be aware of how high the extrinsic pressure might be before management and take steps to minimize complications.

Histone deacetylase inhibition has cardiac and vascular protective effects in rats with pressure overload cardiac hypertrophy

Histone deacetylase (HDAC) inhibitors have shown beneficial effects in animal models of cardiovascular diseases. We hypothesized that HDAC inhibitor, sodium valproate (VPA), has cardiac and vascular protective effects in rats with pressure overload cardiac hypertrophy induced by transverse aortic constriction (TAC). Sections of the heart were visualized after hematoxylin and eosin staining, picrosirius red staining and immunohistochemistry. The expression of genes related to cardiac hypertrophy, fibrosis, and oxidative stress was determined by quantitative real-time polymerase chain reaction. The aortic ring tension analysis was conducted using both the ascending aorta and descending thoracic aorta. TAC increased the expression of hypertrophic, fibrotic, and oxidative stress genes, which was attenuated by VPA. In the ascending aorta with intact endothelium, there was a significant decrease in the relaxation response, which was recovered by VPA treatment. These results indicate that VPA has cardiac and vascular protective effects in rats with pressure overload cardiac hypertrophy.

Upregulation of C/EBPβ and TSC2 by an HDAC inhibitor CG200745 protects heart from DOCA-induced hypertrophy

Histone deacetylases (HDACs) are a vast family divided into four major classes: class I (1, 2, 3, and 8), class II (4, 5, 6, 7, 9 and 10), class III (sirtuin family) and class IV (HDAC11). HDAC inhibition attenuates cardiac hypertrophy through suppression of the mechanistic target of rapamycin complex1 (mTORC1) signaling. HDAC inhibitors upregulate the expression of tuberous sclerosis complex 2 (TSC2), an mTORC1 inhibitor. However, the molecular mechanism underlying HDAC inhibitor-mediated upregulation of TSC2 is unclear. We hypothesized that an HDAC inhibitor, CG200745 (CG), ameliorates cardiac hypertrophy through the inhibition of mTORC1 signaling by upregulating of the CCAAT/enhancer-binding protein-β (C/EBP-β)/TSC2 pathway. To establish a cardiac hypertrophy model, deoxycorticosterone acetate (DOCA, 40 mg/kg/wk) was subcutaneously injected for 4 weeks into Sprague-Dawley rats. All rats were unilaterally nephrectomized and had free access to drinking water containing 1% NaCl with or without CG of different concentrations. The expression level of TSC2 and C/EBP-β was measured by quantitative real-time PCR (qRT-PCR) and western blot analysis. Acetylation of C/EBP-β was analyzed by immunoprecipitation. The recruitment of C/EBP-β and polymerase II (Pol II) on TSC2 promoter region was analyzed by chromatin immunoprecipitation (ChIP). CG treatment increased the expression of TSC2. In addition, CG treated rats showed an increased in the expression and acetylation of C/EBP-β, owing to the increase in the recruitment of C/EBP-β and Pol II at Tsc2 gene promoter. Thus, CG ameliorates cardiac hypertrophy through the inhibition of mTORC1 signaling via upregulation of the C/EBP-β/TSC2 pathway in DOCA-induced hypertensive rats.

Video-Assisted Thoracoscopic Left Cardiac Sympathetic Denervation in Patients with Hereditary Ventricular Arrhythmias

BACKGROUND

Left cardiac sympathetic denervation (LCSD) has been underutilized in patients with hereditary ventricular arrhythmia syndromes such as congenital long QT syndrome (LQTS) and catecholaminergic polymorphic ventricular tachycardia (CPVT). The purpose of this study was to investigate the safety and efficacy of video-assisted thoracoscopic (VATS) LCSD in such patients.

METHODS

Fifteen patients (four men, 24.6 ± 10.5 years old) who underwent VATS-LCSD between November 2010 and January 2015 for hereditary ventricular arrhythmia syndromes at Kyungpook National University Hospital were enrolled in this study. The safety and efficacy of VATS-LCSD were evaluated by periprocedural epinephrine tests and assessing the development of complications and cardiac events during follow-up.

RESULTS

Fourteen patients with LQTS and one patient with CPVT underwent VATS-LCSD. Six and one patients developed ventricular tachyarrhythmia during preprocedural and postprocedural epinephrine test, respectively (P = 0.063). No serious complications such as Horner syndrome, pneumothorax, or bleeding developed after LCSD. Mean hospital stay after VATS-LCSD was 3.7 ± 1.5 days. During a mean follow-up of 927 ± 350 days, one LQTS patient and one CPVT patient, neither of whom manifested tachyarrhythmia during post-LCSD epinephrine test, developed torsades de pointes and syncope, respectively. The annual event rates of six patients who were symptomatic during the period preceding LCSD decreased from 0.97 to 0.19 events/year (P = 0.045).

CONCLUSIONS

VATS-LCSD was a safe, and effective procedure for patients with hereditary ventricular tachycardia syndrome, with no serious adverse events and with short hospital stay.

Bunch-by-bunch position measurement and analysis at PLS-II

A bunch-by-bunch measurement system has been developed at Pohang Light Source II. The system consists of a four-channel button pick-up, 20 GHz sampling oscilloscope and an 800 MHz low-pass digital filter. Upon measuring a bunch-by-bunch spatio-temporal beam motion matrix over many turns, singular-value decomposition analysis is used to reveal the dominant coupled-bunch modes. The system can diagnose injection oscillations due to kicker errors and the effect of resistive-wall impedance that gives rise to instability during operation.

Localized insulin amyloidosis with use of concentrated insulin: a potential complication

BACKGROUND

Insulin-derived amyloidosis is a rare form of amyloidosis composed of insulin fibrils. The pH and concentration of insulin are known to influence the conformational state of the insulin hormone, with an increasing concentration favouring a more complex conformation. Concentrated insulin delivers a large amount of insulin to a localized area, raising the possibility of inducing conformational changes, forming insulin fibrils and leading to localized insulin amyloidosis.

CASE REPORT

A middle-aged woman with long history of Type 2 diabetes mellitus, treated with concentrated human insulin (U-500 insulin) presented with nodular lesions at the site of her daily insulin injections. A punch biopsy of the nodules showed skin with dermal amyloidosis staining favourably with Congo Red stain. The amyloid tumours were resected and areas positive for Congo Red stain were sent for liquid chromatography tandem mass spectrometry, which showed a peptide profile consistent with amyloid insulin.

CONCLUSION

Concentrated insulin was first introduced in 1952, however, it is only over the last two decades that it has been used increasingly, in congruence with the increasing incidence of obesity and diabetes mellitus seen in the USA. Only a few cases of insulin amyloidosis at the site of injection have been described in literature. With the increase in the use of insulin, this complication seems to be occurring more frequently. This is the first case report of a person with diabetes mellitus who developed localized insulin amyloidosis with the use of concentrated insulin, and points towards a potential complication of developing insulin amyloidosis with the use of concentrated insulin.

Fourth Recurrence of Cardiac Myxoma in a Patient with the Carney Complex

Although cardiac myxoma is the most commonly encountered benign cardiac tumor in cardiac surgery practice, recurrent cardiac myxoma is very rare, is most commonly related to the Carney complex, and usually requires multiple cardiac operations with specific requirements in terms of perioperative management. In this report, we describe a patient who experienced the fourth recurrence of cardiac myxoma and review the diagnostic criteria of the Carney complex. This is the first report of such a case in Korea.

Staged Management of a Ruptured Internal Mammary Artery Aneurysm

The rupture of an internal mammary artery (IMA) aneurysm in a patient with type 1 neurofibromatosis (NF-1) is a rare but life-threatening complication requiring emergency management. A 50-year-old man with NF-1 was transferred to the emergency department of Kyungpook National University Hospital, where an IMA aneurysmal rupture and hemothorax were diagnosed and drained. The IMA aneurysmal rupture and hemothorax were successfully repaired by staged management combining endovascular treatment and subsequent video-assisted thoracoscopic surgery (VATS). The patient required cardiopulmonary cerebral resuscitation, the staged management of coil embolization, and a subsequent VATS procedure. This staged approach may be an effective therapeutic strategy in cases of IMA aneurysmal rupture.

Adherence with renal dosing recommendations in outpatients undergoing haemodialysis

WHAT IS KNOWN AND OBJECTIVE

Adjustment of drug dosage in patients with end-stage renal disease prevents serious adverse effects, which occur due to the accumulation of drugs or other toxic metabolites. Nevertheless, dosing errors occur most commonly among patients with end-stage renal disease. The aim of this study was to assess the quality of care for end-stage renal disease outpatients using their renal dosing adjustment status.

METHODS

A cross-sectional study was performed using the data collected from 43 South Korean medical institutions via questionnaires. A total of 2428 patients on haemodialysis, who were at least 18 years of age, were included. Among these patients, the study population was confined to patients who were taking medications and required renal dosing adjustments from three therapeutic classes: antihypertensives, antihyperglycaemics and lipid-modifying agents. The study population (n = 828) was prescribed a total of 1097 drug orders for the target drugs. Determination of appropriate dosage adjustment was based on GFR (glomerular filtration rate) using the Modification of Diet in Renal Disease revised 4-variable equation. The primary outcome was non-adherence to drug dosing requirements for end-stage renal disease patients with consideration to their renal function.

RESULTS AND DISCUSSION

Among the study population (n = 828), 469 haemodialysis patients were identified as having drug orders that were adherent to renal dosing recommendations. There were significant differences between the patient groups who received recommendation-adherent and non-adherent drug orders in the characteristics of the medical institutions they visited, causes of chronic renal failure and prevalence of concurrent diabetes mellitus. The primary factor of non-adherence to renal dosing adjustment recommendations was characteristics of medical institutions. Compared to tertiary hospitals, secondary hospitals and primary care clinics were 1·16 and 1·22 times, respectively, more non-adherent in accordance with the multivariate analysis (OR: 1.16, 95% CI: 1.02-1.20, OR: 1.22, 95% CI: 1·00-1·36, respectively).

WHAT IS NEW AND CONCLUSIONS

Dosing error is one of the most common problems among patients with renal failure. To decrease the dosing errors, an improvement needs to be made in medical institutions. This can be accomplished by implementing the clinical decision support systems that educate physicians on appropriate renal dosing and help them prescribe appropriate drug dosages.

Pseudoaneurysm of surgically reconstructed right ventricular outflow tract complicated by superior vena cava syndrome

Pseudoaneurysm of the right ventricular outflow tract (RVOT) has been reported as a rare complication of RVOT reconstruction performed using conduit replacement or patch repair. Rarely, it may present alongside symptoms secondary to the compression of adjoining mediastinal structures. We report the case of a patient who developed a symptomatic RVOT pseudoaneurysm one month after a total correction of tetralogy of Fallot. In the present case, superior vena cava syndrome was caused by compression of the superior vena cava, which was a very unusual presentation.

Outcomes of nonpledgeted horizontal mattress suture technique for mitral valve replacement

BACKGROUND

Most surgeons favor the pledgeted suture technique for heart valve replacements because they believe it decreases the risk of paravalvular leak (PVL). We hypothesized that the use of nonpledgeted rather than pledgeted sutures during mitral valve replacement (MVR) may decrease the incidence of prosthetic valve endocarditis (PVE) and risk of a major PVL.

METHODS

We analyzed 263 patients, divided into 175 patients who underwent MVR with nonpledgeted sutures from January 2003 to December 2013 and 88 patients who underwent MVR with pledgeted sutures from January 1995 to December 2001. We compared the occurrence of PVL and PVE between these groups.

RESULTS

In patients who underwent MVR with or without tricuspid valve surgery and/or a Maze operation, PVL occurred in 1.1% of the pledgeted group and 2.9% of the nonpledgeted group. The incidence of PVE was 2.9% in the nonpledgeted group and 1.1% in the pledgeted group. No differences were statistically significant.

CONCLUSION

We suggest that a nonpledgeted suture technique can be an alternative to the traditional use of pledgeted sutures in most patients who undergo MVR, with no significant difference in the incidence of PVL.

Korean mistletoe lectin regulates self-renewal of placenta-derived mesenchymal stem cells via autophagic mechanisms

OBJECTIVES

The balance between survival and death is a key point for regulation of physiology of stem cells. Recently, applications of natural products to enhance efficiencies in culturing and differentiation of stem cells are increasing. Korean mistletoe lectin (Viscum album L. var. coloratum agglutinin, VCA) has been known to be toxic to some cancer cells, but it is still unclear whether VCA has a cytotoxic or indeed a proliferative effect on mesenchymal stem cells (MSCs). Here, we have compared effects of VCA in naïve placenta-derived stem cells (PDSCs), immortalized PDSCs and cancer cells (HepG2), and analysed their mechanisms.

MATERIALS AND METHODS

MTT assay was performed to analyse effects of VCA on naïve PDSCs, immortalized PDSCs and HepG2. FACS, ROS, caspase-3 assay, western blotting and immunofluorescence were performed to detect signalling events involved in self-renewal of the above cell types.

RESULTS

VCA had cancer cell-specific toxicity to HepG2 cells even with low concentrations of VCA (1-5 pg/ml), toxicity was observed to immortalized PDSCs and HepG2s, while proliferation of naïve PDSCs was significantly increased (P < 0.05). ROS production by VCA treatment in naïve PDSCs was significantly lower compared to controls (P < 0.05). Furthermore, autophagy was activated in naïve PDSCs treated with VCA through increase in type II LC3 and decrease in phosphorylated mTOR.

CONCLUSIONS

VCA can promote MSC proliferation through an activated autophagic mechanism.

Placement of Endovascular Stent Graft in Acute Malperfusion Syndrome After Acute Type II Aortic Dissection

Acute malperfusion syndrome is a serious complication of acute aortic dissection. A 76-year-old female patient was admitted with acute type B aortic dissection and developed renal malperfusion during medical therapy. We are reporting a clinically successful result from the thoracic endovascular aortic repair used for malperfusion syndrome that occurred by acute type B aortic dissection.

Monoclonal Antibodies against Differentiating Mesenchyme Cells in Larvae of the Ascidian Halocynthia roretzi

Mechanisms of cell specification of mesenchyme during ascidian embryogenesis are poorly understood. This is because no good molecular markers have been available to evaluate differentiation of the mesenchyme cells. To obtain molecular markers of mesenchyme differentiation, we established monoclonal antibodies, Mch-1 and Mch-3, that recognize antigens present in the mesenchyme cells of the larva of Halocynthia roretzi. The antigens recognized by both antibodies start to be detectable in the mesenchyme cells at the late tailbud stage. The Mch-3 antibody specifically recognized all mesenchyme cells of the larva, whereas the Mch-1 antibody stained the cells only in the anterior portions of mesenchyme clusters in the trunk region of the larva. The Mch-1 antibody also stained trunk lateral cells. In addition, both antibodies recognized the mesenchyme cells in the ventro-lateral boundary between endoderm and epidermis that are migrating to the anterior head region of the larva. The partial embryos that originated from the mesenchymelineage cells at the 8-cell stage expressed the Mch-1 and Mch-3 antigens. The Mch-1 and Mch-3 antibodies will be useful as immunological probes for studying the specification mechanisms of mesenchyme cells.

Comparison of the Outcomes between Axillary and Femoral Artery Cannulation for Acute Type A Aortic Dissection

Background

At present, many surgeons prefer axillary artery cannulation because it facilitates antegrade cerebral perfusion and may diminish the risk of cerebral embolization. However, axillary artery cannulation has not been established as a routine procedure because there is controversy about its clinical advantage.

Materials and Methods

We examined 111 patients diagnosed with acute type A aortic dissection between January 2000 and December 2009. The right axillary artery was cannulated in 58 patients (group A) and the femoral artery was cannulated in 53 (group F). The postoperative outcomes were retrospectively reviewed and compared between the two groups.

Results

There were 46 male and 65 female patients with a mean age of 58.9±13.1 years (range, 26 to 84 years). The extent of aortic replacement in both groups did not differ. There were 8 early deaths (7.2%) and 2 late deaths (1.8%). The mean follow-up duration was 46.0±32.6 months (range, 1 month to 10 years). Transient neurologic dysfunction was observed in 11 patients (19.0%) in group A and 14 patients (26.4%) in group F. A total of 11 patients (9.9%) suffered from a permanent neurologic dysfunction. Early and delayed stroke were observed in 6 patients (10.3%) and 2 patients (3.4%), respectively, in group A as well as 2 patients (3.8%) and 1 patient (1.9%), respectively, in group F. There were no statistical differences in the cannulation-related complications between both groups (3 in group A vs. 0 in group F).

Conclusion

There were no differences in postoperative neurologic outcomes and cannulation-related complications according to the cannulation sites. The cannulation site in an aortic dissection should be carefully chosen on a case-by-case basis. It is important to also pay attention to the possibility of intraoperative malperfusion syndrome occurring and the subsequent need to change the cannulation site.

Production of rare isotope beams at the Texas A&M University Cyclotron Institute

The Cyclotron Institute at Texas A&M is currently configuring a scheme for the production of radioactive-ion beams that incorporates a light-ion guide and a heavy-ion guide coupled with an electron-cyclotron-resonance ion source constructed for charge-breeding. This scheme is part of an upgrade to the facility and is intended to produce radioactive beams suitable for injection into the K500 superconducting cyclotron. The current status of the project and details on the ion sources used in the project is presented.

Genetic variation of the HIV-1 integrase region in newly diagnosed anti-retroviral drug-naïve patients with HIV/AIDS in Korea

The survival time of HIV/AIDS patients in Korea has increased since HAART (highly active anti-retroviral therapy) was introduced. However, the occurrence of drug-resistant strains requires new anti-retroviral drugs, one of which, an integrase inhibitor (INI), was approved by the US Food and Drug Administration (FDA) in 2007. INIs have been used for therapy in many countries and are about to be employed in Korea. Therefore, it is important to identify basic mutant variants prior to the introduction of INIs in order to estimate their efficacy. To monitor potential drug-resistant INI mutations in Korean HIV/AIDS patients, the polymorphism of the int gene was investigated together with the pol gene using a genotypic assay for 75 randomly selected Korean HIV-1 patients newly diagnosed in 2007. The drug-resistant mutation sequences were analysed using the Stanford HIV DB and the International AIDS Society resistance testing-USA panel (IAS-USA). Seventy strains of Korean subtype B were compared with foreign subtype-B strains, and there were no significantly different variants of the int gene region in the study population. Major mutation sites in the integrase (E92Q, F121Y, G140A/S, Y143C/R, Q148H/R/K and N155H) were not detected, and only a few minor mutation sites (L74M, V151I, E157Q, V165I, I203M, S230N and D232N) were identified in 21 strains (28%). Resistance due to mutations in the pol gene was observed in a single strain (1.3%) resistant to protease inhibitors (PIs) and in four strains (5.3%) resistant to reverse transcriptase inhibitors (RTIs). In summary, this demonstrates that INIs will be susceptible to drug naïve HIV/AIDS patients in Korea.

Culture and in vitro hepatogenic differentiation of placenta-derived stem cells, using placental extract as an alternative to serum

OBJECTIVES

Translational research using adult stem cells derived from various tissues has been highlighted in cell-based therapy. However, there are many limitations to using conventional culture systems of adult stem cells for clinically applicability, including limited combinations of cytokines and use of nutrients derived from animals. Here, we have investigated the effects of placental extract (PE) for culture of placenta-derived stem cells (PDSCs) as well as their potential for hepatogenic differentiation.

MATERIALS AND METHODS

Placental extract, extracted using water-soluble methods, was used as a supplement for culture of PDSCs. Cell viability was determined using the MTT assay, and cytokine assay was performed using Luminex assay kit. Gene expression, indocyanine green (ICG) up-take, PAS (Periodic Acid-Schiff) staining and urea production were also analysed.

RESULTS

The placental extract contained several types of cytokine and chemokine essential for maintenance and differentiation of stem cells. Expression of stemness markers in PDSCs cultured with PE is no different from that of PDSCs cultured with foetal bovine serum (FBS). After hepatogenic differentiation, expression patterns for hepatocyte-specific markers in PDSCs cultured with PE were consistent and potential for hepatogenic differentiation of PDSCs cultured with PE was similar to that of PDSCs cultured with FBS, as shown by PAS staining and urea production assays.

CONCLUSIONS

Our findings revealed that placental extract could be used as a new component for culture of adult stem cells, as well as for development of human-based medium, in translational research for regenerative medicine.

Preparation of titanium dioxide nanoparticles from electrocoagulated sludge using sacrificial titanium electrodes

A comprehensive investigation of electrocoagulation using sacrificial titanium (Ti) electrodes in wastewater was carried out. The effects of specific process variables, such as initial pH, mixing, current density, initial organic loading, and ionic/electrolyte strength were first optimized to produce recyclable Ti-based sludge. The sludge was incinerated at 600 degrees C to produce functional TiO(2) photocatalyst. X-ray diffraction analysis revealed that TiO(2) produced at optimum electrocoagulation conditions was mostly anatase structure. The specific surface area of the synthesized TiO(2) photocatalyst was higher than that of the commercially available and widely used Degussa P-25 TiO(2). Furthermore, energy dispersive X-ray and X-ray photoelectron spectroscopy analyses showed that in additional to titanium and oxygen, this photocatalyst is also composed of carbon and phosphorus. These elements were mainly doped as a substitute site for the oxygen atom. Transmission electron microscopy images exhibited sharply edged nanorods, round nanoparticles, and nanotubes with nonuniform shapes showing some structural defects. Photodecomposition of gaseous acetaldehyde by this photocatalyst was also conducted under UV and visible light irradiation to study the photocatalytic properties of the doped TiO(2) photocatalyst. While no photocatalytic activity was observed under visible light irradiation, this doped TiO(2) photocatalyst exhibited high photocatalytic activity under UV light.

Decrease of initial CD4+ T-cell counts at the time of diagnosis of HIV infection in Korea; 1988-2006

The aim of the study was to evaluate the trends of initial CD4+ T-cell counts (CD4+) at HIV diagnoses and to identify the factors influencing the annual changes of CD4+ cell counts in Korea during 1988-2006. As a retrospective study, 2613 individuals (>/=15 years at diagnosis, their CD4+ counts were measured within six months) were selected from all 4580 HIV-infected Koreans diagnosed between 1985 and 2006. The mean CD4+ cell counts in all the selected individuals was 312 cells/mm(3), and this value decreased significantly by 20.3 cells/mm(3)/year over the 19 year study period. Men had lower CD4+ cell count than women by 22.7 cells/mm(3), and age at HIV diagnosis had an inverse relationship with CD4+ cell counts of 23.5 cells/mm(3) lower per 10 years advancing age. Cases diagnosed in hospitals showed CD4+ cell count levels 33.9 cells/mm(3) lower than public institutions by 33.9 cells/mm(3). Gender and age seemed to affect trends of CD4+ count; however the institution where cases were diagnosed had the strongest effect on decreasing CD4+ cell counts. The results suggest that HIV diagnoses in recent years are being made in later stages of HIV infection and that it is imperative to develop more efficient programmes for early HIV diagnosis to prevent transmission.

Removal of heavy metals in an abandoned mine drainage via ozone oxidation: a pilot-scale operation

The objective of this study was to evaluate the ozone oxidation of dissolved heavy metals in an abandoned mine drainage (AMD) by conducting a pilot-scale operation at two different ozone doses of 7.5 and 24.0 g O(3)/h into an ozone reactor. A portion of the abandoned mine drainage near the Jungam Mine in Samchuck, Korea was pumped into this pilot-scale plant and used as an influent for the ozone oxidation. Some possible precipitates of metal oxides and hydroxides that resulted from the pilot-scale ozone oxidation of the dissolved Fe and Mn ions in the AMD (with a hydraulic retention time of 106 seconds in the ozone reactor) were effectively removed via sand filtration. A six-hour ozone oxidation with an ozone dose of 24.0 g O(3)/h and subsequent sand filtration, before backwashing the sand filter bed, can meet Korean drinking water quality standards (less than 0.3 mg/L) for Fe and Mn in the sand filter effluent under the operating conditions that were used in this study. The SO(4)(-2) concentrations and alkalinities of the influents were not affected by the ozone oxidation. The pH values of the influents were neutral or slightly alkaline, and after the six-hour oxidation, increased very slightly. These experiment results show that the ozone oxidation of dissolved heavy metals and the subsequent sand filtration of metal precipitates are desirable alternatives to removing heavy metals in an abandoned mine drainage.

A case of coronary artery dissection after aortic replacement in acute type a aortic dissection

A 59-year-old woman was transferred to our institution with a diagnosis of acute type A aortic dissection. During aortic replacement surgery, the dissection had not extended to the orifice of the left coronary artery. However, ST segment elevation was observed on an electrocardiogram monitor immediately postoperatively. An emergent coronary angiogram showed almost complete collapse of the lumen of the left coronary artery due to pulsatile compression of the false lumen, which was caused by extension of the aortic dissection. Percutaneous coronary intervention (PCI) was performed with placement of stents in the left anterior descending artery (LAD) and left circumflex artery. Coronary angiography and intravascular ultrasound performed 45-days after PCI showed significant instent restenosis (ISR) at the proximal portion of the LAD and residual coronary artery dissection of the diagonal branch. Repeat balloon angioplasty was performed at the site of the ISR. A follow-up coronary angiogram 8-months after the PCI showed no evidence of ISR.

Preparation of titanium dioxide (TiO2) from sludge produced by titanium tetrachloride (TiCl4) flocculation of wastewater

Sludge disposal is one of the most costly and environmentally problematic challenges of modern wastewater treatment worldwide. In this study, a new process was developed, which has a significant potential for lower cost of waste disposal, protection of the environment and public health, and yield of economically useful byproducts. Titanium oxide (TiO2), which is the most widely used metal oxide, was produced from the wastewater sludge generated by the flocculation of secondary wastewater with titanium tetrachloride (TiCl4). Detailed analyses were conducted to compare TiCl4, ferric chloride (FeCl3), and aluminum sulfate (Al2(SO4)3) flocculation. Removal of organic matter and different molecular sizes by Ti-salt flocculation was similar to that of the most widely used Fe- and Al-salt flocculation. The mean size of Ti-, Fe-, and Al-salt flocs was 47.5, 42.5, and 16.9 microm, respectively. The decantability of the settled flocs by TiCl4 coagulant was similar to that by FeC13 coagulant and much higher than that of Al2(SO4)3. The photocatalyst from wastewater (PFW) produced by TiCl4 flocculation was characterized by X-ray diffraction, BET surface area, scanning electron microscopy/energy dispersive X-ray, transmission electron microscopy, photocatalytic activity, and X-ray photoelectron spectroscopy. The resulting PFW was found to be superior to commercial TiO2 (P-25) in terms photocatalytic activity and surface area. The PFW as also found to be mainly doped with C and P atoms. The atomic percentage of the PFW was TiO(1.42)C(0.44)P(0.14).

High-level expression and one-step purification of cyclic amidohydrolase family enzymes

The cyclic amidohydrolase family enzymes, including hydantoinase, dihydropyrimidinase, allantoinase and dihydroorotase, are metal-dependent hydrolases and play a crucial role in the metabolism of purine and pyrimidine in prokaryotic and eukaryotic cells. With the increasing demand for the elucidation of enzyme structures and functions, along with industrial applications, the research on the family enzymes has recently been proliferating, but the related enzymes had been purified conventionally by multistep purification procedures. Here, we reported the expression in Escherichia coli cells of maltose-binding protein-fused family enzymes and their one-step purification. The expression levels of the fusion proteins account for 20-35% of the total protein in E. coli, allowing approximately 2-3 mg of the purified proteins by affinity chromatography to be obtained per 0.3 L of bacterial culture. As more promising results, their nascent biochemical properties, after the cleavage of the fusion proteins with Factor Xa, in terms of oligomeric structure, optimal pH, specific activity, and kinetic property, were also conserved as those from the native enzymes. The availability of the family enzymes to fusion strategy shows potential as a convenient procedure to recombinant protein purification and accelerates the structure-function study of the related family enzymes.

Multicenter study of the frequency of contact allergy to gold

Gold sodium thiosulfate (GSTS) is reputed to be the most reliable gold antigen, but control studies are still required. Although Koreans have more varied sources of contact with gold, such as herbal medicines with gold coatings and indwelling gold acupuncture needles, no epidemiological studies have been performed. This study examined the frequency and sources of contact allergy to gold in South Korea by a multicenter study. Patch testing with 0.5% GSTS in pet. was conducted in 255 eczema patients and 58 control subjects. Results were observed at 21 days (D) to ensure there were no undetected late reactions in 54 observed patients and 47 controls. 8 (3.1%) of the 255 patients reacted positively to GSTS, including 1 with a late reaction. 1 of the 58 controls showed a positive reaction to GSTS on D4 with a negative reaction on D14. Clinical relevance was lacking in the patients with positive reactions. Unexpectedly, the above particular sources of gold contact gave rise to few allergic reactions in our patients.

Role of the FGF and MEK signaling pathway in the ascidian embryo

In the ascidian embryo, a fibroblast growth factor (FGF)-like signal from presumptive endoderm blastomeres between the 32-cell and early 64-cell stages induces the formation of notochord and mesenchyme cells. However, it has not been known whether endogenous FGF signaling is involved in the process. Here it is shown that 64-cell embryos exhibit a marked increase in endogenous extracellular signal-regulated kinase (ERK/MAPK) activity. The increase in ERK activity was reduced by treatment with an FGF receptor 1 inhibitor, SU5402, and a MEK (ERK kinase/MAPKK) inhibitor, U0126. Both drugs blocked the formation of notochord and mesenchyme when embryos were treated at the 32-cell stage, but not at the 2- or 110-cell stages. The dominant-negative form of Ras also suppressed notochord and mesenchyme formation. Both inhibitors suppressed induction by exogenous basic FGF. These results suggest that the FGF signaling cascade is indeed necessary for the formation of notochord and mesenchyme cells during ascidian embryogenesis. It is also shown that FGF signaling is required for formation of the secondary notochord, secondary muscle and neural tissues, and at least ERK activity is necessary for the formation of trunk lateral cells and posterior endoderm. Therefore, FGF and MEK signaling are required for the formation of various tissues in the ascidian embryo.

Generation of protein lineages with new sequence spaces by functional salvage screen

A variety of different methods to generate diverse proteins, including random mutagenesis and recombination, are currently available and most of them accumulate the mutations on the target gene of a protein, whose sequence space remains unchanged. On the other hand, a pool of diverse genes, which is generated by random insertions, deletions and exchange of the homologous domains with different lengths in the target gene, would present the protein lineages resulting in new fitness landscapes. Here we report a method to generate a pool of protein variants with different sequence spaces by employing green fluorescent protein (GFP) as a model protein. This process, designated functional salvage screen (FSS), comprises the following procedures: a defective GFP template expressing no fluorescence is first constructed by genetically disrupting a predetermined region(s) of the protein and a library of GFP variants is generated from the defective template by incorporating the randomly fragmented genomic DNA from Escherichia coli into the defined region(s) of the target gene, followed by screening of the functionally salvaged, fluorescence-emitting GFPs. Two approaches, sequence-directed and PCR-coupled methods, were attempted to generate the library of GFP variants with new sequences derived from the genomic segments of E.coli. The functionally salvaged GFPs were selected and analyzed in terms of the sequence space and functional properties. The results demonstrate that the functional salvage process not only can be a simple and effective method to create protein lineages with new sequence spaces, but also can be useful in elucidating the involvement of a specific region(s) or domain(s) in the structure and function of protein.

Chromosomal aberrations in neuroblastoma cell lines identified by cross species color banding and chromosome painting

We have studied cytogenetic rearrangements in karyotypes of five neuroblastoma cell lines [SK-N-AS, SK-N-SH, SH-SY5Y, SK-N-MC, SMS-KCNR] by G-banding, cross species color banding (RxFISH), and fluorescence in situ hybridization (FISH) with chromosome painting probes. Each neuroblastoma cell line had unique modal karyotypic characteristics and showed a variable number of numerical and structural clonal cytogenetic aberrations. The number of rearranged chromosomes in SK-N-AS, SK-N-SH, SH-SY5Y, SK-N-MC, and SMS-KCNR was 11, 3, 7, 14 (tetraploid, 20-21), and 6, respectively. The origins of abnormal chromosomes were effectively analyzed by RxFISH and FISH with multiple chromosome painting probes. The chromosomal origin of the homogeneously staining region in SH-SY5Y was identified as coamplification of chromosome bands 2p13 and 2p24 by chromosome microdissection and FISH. The non-random rearrangements of chromosomes were determined on 1p34 approximately p36, 6q16 approximately q21, 8q24, 9q34, 11q13 approximately q23, 16q23 approximately q24, 17q21, and 22q31. These results may provide useful information for further molecular characterization of neuroblastoma.

Functional expression and characterization of the two cyclic amidohydrolase enzymes, allantoinase and a novel phenylhydantoinase, from Escherichia coli

A superfamily of cyclic amidohydrolases, including dihydropyrimidinase, allantoinase, hydantoinase, and dihydroorotase, all of which are involved in the metabolism of purine and pyrimidine rings, was recently proposed based on the rigidly conserved structural domains in identical positions of the related enzymes. With these conserved domains, two putative cyclic amidohydrolase genes from Escherichia coli, flanked by related genes, were identified and characterized. From the genome sequence of E. coli, the allB gene and a putative open reading frame, tentatively designated as a hyuA (for hydantoin-utilizing enzyme) gene, were predicted to express hydrolases. In contrast to allB, high-level expression of hyuA in E. coli of a single protein was unsuccessful even under various induction conditions. We expressed HyuA as a maltose binding protein fusion protein and AllB in its native form and then purified each of them by conventional procedures. allB was found to encode a tetrameric allantoinase (453 amino acids) which specifically hydrolyzes the purine metabolite allantoin to allantoic acid. Another open reading frame, hyuA, located near 64.4 min on the physical map and known as a UUG start, coded for D-stereospecific phenylhydantoinase (465 amino acids) which is a homotetramer. As a novel enzyme belonging to a cyclic amidohydrolase superfamily, E. coli phenylhydantoinase exhibited a distinct activity toward the hydantoin derivative with an aromatic side chain at the 5' position but did not readily hydrolyze the simple cyclic ureides. The deduced amino acid sequence of the novel phenylhydantoinase shared a significant homology (>45%) with those of allantoinase and dihydropyrimidinase, but its functional role still remains to be elucidated. Despite the unclear physiological function of HyuA, its presence, along with the allantoin-utilizing AllB, strongly suggested that the cyclic ureides might be utilized as nutrient sources in E. coli.

An FGF signal from endoderm and localized factors in the posterior-vegetal egg cytoplasm pattern the mesodermal tissues in the ascidian embryo

The major mesodermal tissues of ascidian larvae are muscle, notochord and mesenchyme. They are derived from the marginal zone surrounding the endoderm area in the vegetal hemisphere. Muscle fate is specified by localized ooplasmic determinants, whereas specification of notochord and mesenchyme requires inducing signals from endoderm at the 32-cell stage. In the present study, we demonstrated that all endoderm precursors were able to induce formation of notochord and mesenchyme cells in presumptive notochord and mesenchyme blastomeres, respectively, indicating that the type of tissue induced depends on differences in the responsiveness of the signal-receiving blastomeres. Basic fibroblast growth factor (bFGF), but not activin A, induced formation of mesenchyme cells as well as notochord cells. Treatment of mesenchyme-muscle precursors isolated from early 32-cell embryos with bFGF promoted mesenchyme fate and suppressed muscle fate, which is a default fate assigned by the posterior-vegetal cytoplasm (PVC) of the eggs. The sensitivity of the mesenchyme precursors to bFGF reached a maximum at the 32-cell stage, and the time required for effective induction of mesenchyme cells was only 10 minutes, features similar to those of notochord induction. These results support the idea that the distinct tissue types, notochord and mesenchyme, are induced by the same signaling molecule originating from endoderm precursors. We also demonstrated that the PVC causes the difference in the responsiveness of notochord and mesenchyme precursor blastomeres. Removal of the PVC resulted in loss of mesenchyme and in ectopic notochord formation. In contrast, transplantation of the PVC led to ectopic formation of mesenchyme cells and loss of notochord. Thus, in normal development, notochord is induced by an FGF-like signal in the anterior margin of the vegetal hemisphere, where PVC is absent, and mesenchyme is induced by an FGF-like signal in the posterior margin, where PVC is present. The whole picture of mesodermal patterning in ascidian embryos is now known. We also discuss the importance of FGF induced asymmetric divisions, of notochord and mesenchyme precursor blastomeres at the 64-cell stage.

Production of D-amino acid using whole cells of recombinant Escherichia coli with separately and coexpressed D-hydantoinase and N-carbamoylase

We developed a fully enzymatic process employing D-hydantoinase and N-carbamoylase for the production of D-amino acid from 5'-monosubstituted hydantoin. For the comparison of the reaction systems using two sequential enzymes, D-hydantoinase of Bacillus stearothermophilus SD1 and N-carbamoyl-D-amino acid amidohydrolase (N-carbamoylase) of Agrobacterium tumefaciens NRRL B11291 were separately expressed in each host cell and coexpressed in the same host cell. A high level and constitutive expression of both enzymes in Escherichia coli in a soluble form was achieved using a promoter derived from B. stearothermophilus SD1. The expression levels of both enzymes ranged from 17% to 23% of the total soluble protein, depending on the expression system. In the case of employing separately expressed enzymes, the product yield of D-hydroxyphenylglycine from D,L-p-hydroxyphenylhydantoin and productivity were 71% and 2.57 mM/g-cell/h in 15 h, respectively. The accumulation of N-carbamoyl-D-hydroxyphenylglycine was significant over the reaction time. On the other hand, use of coexpressed enzymes resulted in 98% product yield of D-hydroxyphenylglycine in 15 h, minimizing the level of intermediates in the reaction mixture. The productivity of coexpressed whole cell reaction was estimated to be 6.47 mM/g-cell/h in 15 h. The coexpressed system was tested for an elevated concentration of D,L-p-hydroxyphenylhydantoin, and efficient production can be achieved.

Asymmetric modular synthesis of cylindrically chiral FerroPHOS ligands for the Rh-catalyzed asymmetric hydroboration

Asymmetric modular synthesis of air-stable ferrocenyl bisphosphine ligands with cylindrical chirality was achieved employing asymmetric catalytic methods and these chiral ligands were screened in asymmetric hydroboration reaction.

Construction and evaluation of a novel bifunctional N-carbamylase-D-hydantoinase fusion enzyme

A fully enzymatic process employing two sequential enzymes, D-hydantoinase and N-carbamylase, is a typical case requiring combined enzyme activity for the production of D-amino acids. To test the possibility of generating a bifunctional fusion enzyme, we constructed a fusion protein via end-to-end fusion of a whole gene that encodes an intact protein at the N terminus of the D-hydantoinase. Firstly, maltose-binding protein (MBP) gene of E. coli was fused with D-hydantoinase gene from Bacillus stearothermophilus SD1, and the properties of the resulting fusion protein (MBP-HYD) were compared with those of native D-hydantoinase. Gel filtration and kinetic analyses clearly demonstrated that the typical characteristics of D-hydantoinase are maintained even in a fusion state. Based on this result, we constructed an artificial fusion enzyme composed of the whole length of N-carbamylase (304 amino acids [aa]) from Agrobacterim radiobacter NRRL B11291 and D-hydantoinase (471 aa). The fusion enzyme (CAB-HYD) was functionally expressed with an expected molecular mass of 86 kDa and efficiently converted exogenous hydantoin derivatives to the D-amino acids. A related D-hydantoinase (HYD1) gene from Bacillus thermocatenulatus GH2 was also fused with the N-carbamylase gene at its N terminus. The resulting enzyme (CAB-HYD1) was bifunctional as expected and showed better performance than the CAB-HYD fusion enzyme. The conversion of hydantoin derivatives to corresponding amino acids by the fusion enzymes was much higher than that by the separately expressed enzymes, and comparable to that by the coexpressed enzymes. Thus, the fusion enzyme might be useful as a potential biocatalyst for the production of nonnatural amino acids.

Directed evolution of a novel N-carbamylase/D-hydantoinase fusion enzyme for functional expression with enhanced stability

Bifunctional enzymes find a wide application as a monitoring facility and a potential biocatalyst in molecular biology and biotechnology. Recombination of natural enzymes to a bifunctional fusion offers valuable tools, but the functional and structural instability of artificial fusion enzymes remains to be solved. Based on structural traits of microbial D-hydantoinase, we attempted to construct a bifunctional N-carbamylase/D-hydantoinase fusion enzyme that would be useful for the synthesis of nonnatural D-amino acids in a concerted fashion. The bifunctional ability of D-hydantoinase, as a fusion partner, was noticeable, but the resulting fusion enzyme was subjected to serious proteolysis in vivo, as generally encountered in the expression of large the multidomain polypeptide in E. coli. In an effort to improve the structural instability imposed by artificial linear fusion, directed evolution of the fusion enzyme was performed using DNA shuffling with a consensus primer to maintain a crucial domain for the enzyme activity. The evolved fusion enzyme, F11, was selected after repeated rounds, and this enzyme was found to show sixfold increased performance in the production of D-amino acid compared with the parent fusion enzyme, which was mainly due to the enhanced structural stability of the evolved fusion enzyme. This result is an example showing that directed evolution of the linearly fused polypeptide may broaden the opportunity to generate a fusion enzyme with greater potential.

Suppression of muscle fate by cellular interaction is required for mesenchyme formation during ascidian embryogenesis

The tadpole larva of the ascidian Halocynthia roretzi has several hundred mesenchyme cells in its trunk. Mesenchyme cells are exclusively derived from the B8.5 and B7.7 blastomere pairs of the 110-cell embryo. It has been believed that specification of mesenchyme cells is an autonomous process. In the present study, we have demonstrated that presumptive-mesenchyme blastomeres isolated from early 32-cell embryos did not express mesenchyme-specific features, whereas those isolated after the late 64-cell stage developed mesenchyme markers autonomously. Results of experiments involving coisolation and recombination of blastomeres showed that cellular interaction with adjacent presumptive-endoderm blastomeres during the late 32- and early 64-cell stages is required for mesenchyme formation. When such interaction was absent, the presumptive-mesenchyme blastomeres developed into muscle cells. Therefore, a signal from endoderm precursor blastomeres promotes mesenchyme fate, suppressing the muscle fate that is specified by ooplasmic muscle determinants. In Halocynthia, the muscle actin gene was precociously activated in mesenchyme-muscle precursor blastomeres at the 32-cell stage, and the mesenchyme and muscle fates were separated into two daughter blastomeres at the next cleavage. In presumptive-mesenchyme blastomeres at the 64-cell stage, expression of the muscle actin gene was immediately down-regulated by the signal from the neighboring endoderm precursor blastomeres. Thus, mesenchyme formation involves a novel mechanism of fate specification in ascidians, where formation of mesenchyme cells requires cellular interaction that suppresses muscle fate in the mesenchyme precursor blastomeres.

Modeling, simulation, and kinetic analysis of a heterogeneous reaction system for the enzymatic conversion of poorly soluble substrate

We developed a kinetic model that describes a heterogeneous reaction system consisting of a solid substrate suspension for the production of D-amino acid using D-hydantoinase. As a biocatalyst, mass-produced free and whole cell enzymes were used. The heterogeneous reaction system involves dissolution of a solid substrate, enzymatic conversion of the dissolved D-form substrate, spontaneous racemization of an L-form substrate to D-form, and deactivation of the enzyme. In the case of using whole cell enzymes, transfer of the dissolved substrate and product through the cell membrane was considered. The kinetic parameters were determined from experiments, literature data, and by using Marquardt's method of nonlinear regression analysis. The model was simulated using the kinetic parameters and compared with experimental data, and a good agreement was observed between the experimental results and the simulation ones. Factors affecting the kinetics of the heterogeneous reaction system were analyzed on the basis of the kinetic model, and the efficiency of the reaction systems using free and whole cell enzymes was also compared.

Purification and Characterization of Thermostable D-Hydantoinase from Bacillus thermocatenulatus GH-2

A thermostable D-hydantoinase was isolated from thermophilic Bacillus thermocatenulatus GH-2 and purified to homogeneity by using immunoaffinity chromatography. The molecular mass of the enzyme was determined to be about 230 kDa, and a value of 56 kDa was obtained as a molecular mass of the subunit on sodium dodecyl sulfate-polyacrylamide gel electrophoresis, implying that oligomeric structure of the enzyme is tetrameric. Isoelectric pH of the enzyme was found to be approx 4.3. The enzyme required Mn2+ for the activity and exhibited its highest activity with phenylhydantoin as a substrate. The optimal pH and temperature for catalytic activity were about 7.5 and 65 degrees C, respectively. The half-life of the enzyme was estimated to be about 45 min at 80 degrees C.

Identification of the structural similarity in the functionally related amidohydrolases acting on the cyclic amide ring

The functionally related amidohydrolases, including D-hydantoinases, dihydropyrimidinases, allantoinases and dihydro-orotases, share a similar catalytic function of acting on the cyclic amide ring. We aligned 16 amidohydrolases by taking account of the conservative substitution and found a number of highly conserved regions and invariant amino acid residues. Analyses of the secondary structure and hydropathy profile of the enzymes revealed a significant degree of similarity in the conserved regions. Among the regions, the long stretched region I is of particular interest, because it is mainly composed of invariant amino acid residues, showing a similarity of 69% for the enzymes. A search of the protein data bank using the sequence of the conserved region I identified a number of proteins possessing a similar catalytic property, providing a clue that this region might be linked with the catalytic function. As a particular sequence, one aspartic acid and four histidine residues are found to be rigidly conserved in the functionally related amidohydrolases. In order to investigate the significance of the conserved residues, site-directed mutagenesis was carried out typically for the D-hydantoinase gene cloned from Bacillus stearothermophilus SD1. These residues were found to be essential for metal binding as well as catalysis, strongly implying that these invariant residues play a critical role in other enzymes as well as in D-hydantoinase. On the basis of the similar catalytic function and existence of the rigidly conserved sequence, we propose a close evolutionary relationship among the functionally related amido hydrolases, including D-hydantoinase, dihydropyrimidinase, allantoinase and dihydroorotase.