Iodine contrast volume reduction in preoperative transcatheter aortic valve implantation computed tomography: Comparison with 64- and 256-multidetector row computed tomography

INTRODUCTION

This study aimed to compare the vascular enhancement and radiation dose in preoperative transcatheter aortic valve implantation (TAVI) computed tomography (CT) with a reduced contrast medium (CM) using volume scans in 256-multidetector row CT (MDCT) with a standard CM using 64-MDCT.

METHODS

This study included 78 patients with preoperative TAVI CT with either 64- or 256-MDCT. The CM was injected at 1.5 mL/kg in the 64-MDCT group and 1.0 mL/kg in the 256-MDCT group. We compared vascular enhancement of the aortic root and access routes, image quality (IQ) scores, and radiation dose in both groups.

RESULTS

Despite the reduced CM (by 33 %) in the 256-MDCT group, the mean vascular enhancement of the right and left subclavian arteries was significantly higher than that in the 64-MDCT group [284 and 267 Hounsfield units (HU) vs. 376 and 359 HU; p < 0.05]; however, no significant differences in the mean vascular enhancement in the ascending aorta, abdominal aorta at the celiac level, and bilateral common femoral arteries were observed between the two groups (p > 0.05 for all). The median IQ scores at the aortic root were higher in the 256-MDCT group than in the 64-MDCT group (3 vs. 4; p < 0.05), and those at the femoral access routes were comparable (4 vs. 4; p = 0.33). The mean effective dose was significantly reduced by 30 % in the 256-MDCT group (23.6 vs. 16.3 mSv; p < 0.05).

CONCLUSION

In preoperative TAVI CT, volume scans using 256-MDCT provide comparable or better vascular enhancement and IQ with a 30 % reduction in CM and radiation dose than those using 64-MDCT.

IMPLICATIONS FOR PRACTICE

Volume scan using 256-MDCT for preoperative TAVI CT may reduce CM and radiation dose in TAVI patients with renal dysfunction.

Enhancement rate of venous phase to portal venous phase computed tomography and its correlation with ultrasound elastography determination of liver fibrosis

INTRODUCTION

This study aimed to compare the correlation between the computed tomography (CT) enhancement rate of the venous to portal venous phase (VP-ER) and the extracellular volume (ECV) fraction with shear-wave ultrasound elastography (USE) findings in patients with liver fibrosis.

METHODS

We included 450 patients with clinically suspected liver cirrhosis who underwent triphasic dynamic CT studies and USE. We compared the USE results with the unenhanced CT phase, with enhancement in the hepatic artery phase (HAP), portal venous phase (PVP), and venous phase (VP), and with the ECV fraction and the VP-ER. We also compared the area under the curve (AUC) of the receiver operating characteristic (ROC) curve of the ECV fraction and VP-ER with that of the values obtained with USE.

RESULTS

The VP-ER was the most highly correlated with the liver stiffness value determined with USE (Pearson's correlation coefficient: r = 0.37), followed by enhancement in the PVP (r = -0.25), CT number on unenhanced CT scans (r = -0.22), the ECV fraction (r = 0.19), enhancement in the VP (r = 0.059), and enhancement in the HAP (r = -0.023) (all p < 0.01). The VP-ER showed a significantly higher AUC than the ECV fraction (0.75 vs 0.62) when the liver stiffness was >15 kPa in USE studies (p = 0.04).

CONCLUSION

Compared to the ECV fraction, the VP-ER is more useful for predicting all degrees of liver fibrosis on routine triphasic dynamic CT images.

IMPLICATIONS FOR PRACTICE

Although improvement is needed, the VP-ER has a higher diagnostic ability for liver fibrosis than the ECV fraction in clinical practice.

The combined application of the contrast-to-noise index and 80 kVp for cardiac CTA scanning before atrial fibrillation ablation reduces radiation dose exposure

INTRODUCTION

To compare the radiation dose, diagnostic accuracy, and the resultant ablation procedures using 80 and 120-kVp cardiac computed tomography angiography (CCTA) protocols with the same contrast-to-noise ratio in patients scheduled for atrial fibrillation (AF) ablation.

METHODS

This retrospective study was performed following institutional review board approval. We divided 140 consecutive patients who had undergone CCTA using a 64-MDCT scanner into two equal groups. Standard deviation (SD) of the CT number was set at 25 Hounsfield units (HU) for the 120-kVp protocol. To facilitate a reduction in radiation dose it was set at 40 HU for the 80 kVp protocol. We compared the two protocols with respect to the radiation dose, the diagnostic accuracy for detecting left atrial appendage (LAA) thrombi, matching for surface registration, and the resultant ablation procedures.

RESULTS

At 120 kVp, the dose length product (DLP) was 2.2 times that at 80 kVp (1269.0 vs 559.0 mGy cm, p < 0.01). The diagnostic accuracy for thrombus detection was 100% using both protocols. There was no difference between the two protocols with respect to matching for surface registration. The protocols did not differ with respect to the subsequent time required for the ablation procedures and the ablation fluoroscopy time, and the radiation dose (p = 0.54, 0.33, and 0.32, respectively).

CONCLUSION

For the same CNR, the DLP at 80 kVp (559.0 mGy cm) was 56% of that delivered at 120 kVp (1269.0 mGy cm). There was no reduction in diagnostic accuracy.

IMPLICATIONS FOR PRACTICE

Maintaining CNR allows for a reduction in the radiation dose without reducing the image quality.

Utility of osteopontin in cerebrospinal fluid as a diagnostic marker for neuropsychiatric systemic lupus erythematosus

The whole protein of osteopontin (OPN full) and its cleaved form (OPN N-half) are involved in the immune response and the migration of immune cells to an inflammatory lesion. We have reported that serum OPN full and urine OPN N-half are elevated in lupus nephritis (LN). Neuropsychiatric systemic lupus erythematosus (NPSLE) is a refractory complication of SLE. To investigate whether OPN full and OPN N-half could serve as diagnostic markers for NPSLE, and to elucidate their role in NPSLE pathogenesis, the concentrations of OPN full and OPN N-half in cerebrospinal fluid (CSF) were measured in NPSLE and non-NPSLE patients. We found that the concentration of OPN full in the CSF was significantly higher in NPSLE than in non-NPSLE, and it decreased after treatment. When the cutoff value of OPN full in CSF was set to 963.4 ng/ml, the sensitivity and specificity for the diagnosis of NPSLE were 70% and 100%, respectively. The correlation analysis of OPN full, OPN N-half and various cytokines/chemokines suggested that the cytokines/chemokines could be divided into two clusters: cluster A, which contains OPN full and cluster B, which contains interleukin-6. OPN full in CSF could be a novel diagnostic marker for NPSLE.

Non-magnetic flexible heaters for spin-exchange optical pumping of 3He and other applications

Spin polarized ³He gas is currently widely used in various scientific fields and in medical diagnosis applications. The spin polarization of ³He nuclei can be achieved by spin-exchange optical pumping (SEOP). In SEOP, the ³He gas is enclosed in a glass cell together with alkali metals and is then heated to maintain the alkali metal vapor pressures at the appropriate levels. However, polarized ³He gas is highly sensitive to any inhomogeneity in its magnetic field, and any small field gradients caused by the heaters may cause degradation of the ³He polarization. To overcome this conflict between the heating process and the magnetic field, we have developed electrical heaters that essentially cause no magnetic fields. These heaters are thin and are flexible enough to be bent to within a radius of a few centimeters. These carefully designed heater elements and a double layer structure effectively eliminate magnetic field generation. The heaters were originally developed for SEOP applications, but can also be applied to other processes that need to avoid unwanted magnetic fields.

Development of in situ energetic ion injector for magnetically confined plasmas using hydrogen storage electrode

To develop a compact ion injector made of hydrogen storage material, we investigate a plasma response for a positively biased hydrogen storage electrode in a small standard heliac device. When the bias voltage of the electrode increases, a positive potential between the electrode and the space potential on the magnetic surface emerges. The emission of hydrogen atom line also increases. To clarify the origin of the increase in emission, we designed an imaging system with sufficient temporal resolution.

Effect of the C-terminal domain of Vibrio proteolyticus chitinase A on the chitinolytic activity in association with pH changes

AIMS

To reveal the cause of the difference in activity of chitinase A from Vibrio proteolyticus and chitinase A from a strain of Vibrio carchariae (a junior synonym of Vibrio harveyi), we investigated the pH-dependent activity of full-length V. proteolyticus chitinase A and a truncated recombinant corresponding to the V. harveyi form of chitinase A.

METHODS AND RESULTS

After overexpression in Escherichia coli strain DH5α, the full-length and truncated recombinant chitinases were purified by ammonium sulphate precipitation and anion exchange column chromatography. Chitinase activity was measured at various pH values using α-crystal and colloidal chitins as the substrate. The pH-dependent patterns of the relative specific activities for α-crystal chitin differed between the full-length and truncated recombinant chitinases, whereas those for colloidal chitin were similar to each other.

CONCLUSION

The difference in the activity of V. proteolyticus chitinase A and V. harveyi chitinase A might be partly due to a change in the pH dependence of the chitinase activities against α-crystal chitin, resulting from C-terminal processing.

SIGNIFICANCE AND IMPACT OF STUDY

The present results are important findings for not only ecological studies on the genus Vibrio in association with survival strategies, but also phylogenetic studies.

Heterodisaccharide 4-O-(N-acetyl-β-D-glucosaminyl)-D-glucosamine is an effective chemotactic attractant for Vibrio bacteria that produce chitin oligosaccharide deacetylase

AIMS

To investigate the attractant effect of 4-O-(N-acetyl-β-D-glucosaminyl)-D-glucosamine (GlcNAc-GlcN) in the chemotaxis of Vibrio bacteria that produce carbohydrate esterase (CE) family 4 chitin oligosaccharide deacetylase (COD), an enzyme that catalyzes the production of GlcNAc-GlcN from N,N'-diacetylchitobiose (GlcNAc)(2).

METHODS AND RESULTS

The chemotactic effect of disaccharides from chitin on several strains of Vibrio bacteria was investigated using an agar gel lane-migration method. The results demonstrated that GlcNAc-GlcN functions as an effective chemoattractant in the CE family 4 COD-producing vibrios, Vibrio parahaemolyticus and Vibrio alginolyticus. In contrast, this phenomenon was not observed in Vibrio nereis or Vibrio furnissii, which lack genes encoding this enzyme. From transmission electron microscope observation of V. parahaemolyticus cells following the chemotaxis assay, GlcNAc-GlcN appears to stimulate polar flagellum rotation.

CONCLUSIONS

GlcNAc-GlcN is a specific chemoattractant for the CE family 4 COD-producing vibrios, V. parahaemolyticus and V. alginolyticus.

SIGNIFICANCE AND IMPACT OF THE STUDY

It was clarified for the first time that GlcNAc-GlcN functions as a signalling molecule in the chemotaxis of Vibrio bacteria that have an ability to produce CE family 4 COD, which generate GlcNAc-GlcN from (GlcNAc)(2).

Heterodisaccharide 4-O-(N-acetyl-beta-D-glucosaminyl)-D-glucosamine is a specific inducer of chitinolytic enzyme production in Vibrios harboring chitin oligosaccharide deacetylase genes

Vibrio parahaemolyticus KN1699 produces 4-O-(N-acetyl-beta-d-glucosaminyl)-d-glucosamine (GlcNAc-GlcN) as a major end product from chitin using two extracellular hydrolases: glycoside hydrolase family 18 chitinase, which produces (GlcNAc)(2) from chitin, and carbohydrate esterase (CE) family 4 chitin oligosaccharide deacetylase (COD), which hydrolyzes the N-acetyl group at the reducing-end GlcNAc residue of (GlcNAc)(2). In this study, we clarified that this heterodisaccharide functions as an inducer of the production of the two above-mentioned chitinolytic enzymes, particularly chitinase. Similar results for chitinase production were obtained with other chitin-decomposing Vibrio strains harboring the CE family 4 COD gene; however, such an increase in chitinase production was not observed in chitinolytic Vibrio strains that did not harbor the COD gene. These results suggest that GlcNAc-GlcN is a unique inducer of chitinase production in Vibrio bacteria that have the COD-producing ability and that the COD involved in the synthesis of this signal compound is one of the key enzymes in the chitin catabolic cascade of these bacteria.

Design and screening strategies for alpha-glucosidase inhibitors based on enzymological information

Alpha-glucosidase inhibitors are marketed as therapeutic drugs for diabetes that act through the inhibition of carbohydrate metabolism. Inhibitors of the alpha-glucosidases that are involved in the biosynthesis of N-linked oligosaccharide chains have been reported to have antitumor, antiviral, and apoptosis-inducing activities, and some have been used clinically. alpha-Glucosidase inhibitors have interesting biological activities, and their design, synthesis, and screening are being actively performed. In quite a few reports, however, alpha-glucosidases with different origins than the target alpha-glucosidases, have been used to evaluate inhibitory activities. There might be confusion regarding the naming of alpha-glucosidases. For example, the term alpha-glucosidase is sometimes used as a generic name for alpha-glucoside hydrolases. Moreover, IUBMB recommends the use of "alpha-glucosidase" (EC 3.2.1.20) for exo-alpha-1,4-glucosidases, which are further classified into four families based on amino acid sequence similarities. Accordingly, substrate specificity and susceptibility to inhibitors varies markedly among enzymes in the IUBMB alpha-glucosidases. The design and screening of inhibitors without consideration of these differences is not efficient. For the development of a practical inhibitor that is operational in cells, HTS using the target alpha-glucosidase and the computer-aided design of inhibitors based on enzymatic information concerning the same alpha-glucosidase are essential.

Cloning, expression and purification of cytochrome c(6) from the brown alga Hizikia fusiformis and complete X-ray diffraction analysis of the structure

The primary sequence of cytochrome c(6) from the brown alga Hizikia fusiformis has been determined by cDNA cloning and the crystal structure has been solved at 1.6 A resolution. The crystal belonged to the tetragonal space group P4(1)2(1)2, with unit-cell parameters a = b = 84.58, c = 232.91 A and six molecules per asymmetric unit. The genome code, amino-acid sequence and crystal structure of H. fusiformis cytochrome c(6) were most similar to those of red algal cytochrome c(6). These results support the hypothesis that brown algae acquired their chloroplasts via secondary endosymbiosis involving a red algal endosymbiont and a eukaryote host.

Expression of the algal cytochrome c6 gene in Arabidopsis enhances photosynthesis and growth

Photosynthetic plants convert light energy into ATP and NADPH in photosynthetic electron transfer and photophosphorylation, and synthesize mainly carbohydrates in the Calvin-Benson cycle. Here we report the enhancement of photosynthesis and growth of plants by introducing the gene of an algal cytochrome c6, which has been evolutionarily eliminated from higher plant chloroplasts, into the model plant Arabidopsis thaliana. At 60 d after planting, the plant height, leaf length and root length of the transformants were 1.3-, 1.1- and 1.3-fold those in the wild-type plants, respectively. At the same time, in the transgenic plants, the amounts of chlorophyll, protein, ATP, NADPH and starch were 1.2-, 1.1-, 1.9-, 1.4- and 1.2-fold those in the wild-type plants, respectively. The CO2 assimilation capacity of the transgenic plants was 1.3-fold that of the wild type. Moreover, in transgenic Arabidopsis expressing algal cytochrome c6, the 1-qP, which reflects the reduced state of the plastoquinone pool, is 30% decreased compared with the wild type. These results show that the electron transfer of photosynthesis of Arabidopsis would be accelerated by the expression of algal cytochrome c6. Our results demonstrate that the growth and photosynthesis of Arabidopsis plants could be enhanced by the expression of the algal cytochrome c6 gene.

Identification of a novel endochitinase from a marine bacterium Vibrio proteolyticus strain No. 442

Chitin binding proteins prepared from Vibrio proteolyticus were purified and the N-terminal amino-acid sequence of a protein from a 110-kDa band on SDS-PAGE was found to be 85-90% identical to the 22nd-41st residues of the N-termini of chitinase A precursor proteins from other vibrios. We cloned the corresponding gene, which encodes a putative protein of 850 amino acids containing a 26-residue signal sequence. The chitinase precursor from V. proteolyticus was 78-80% identical to those from Vibrio parahaemolyticus, Vibrio alginolyticus and Vibrio carchariae. However, the proteolytic cleavage site for C-terminal processing between R597 and K598 in the chitinase precursor of other vibrios was not observed in the amino acid sequence of V. proteolyticus, which instead had the sequence R600 and A601. Subsequently, full-length and truncated chitinases were generated in Escherichia coli. The specific activity of full-length chitinase expressed in E. coli was 17- and 20-folds higher for colloidal and alpha-chitins (insoluble substrate), respectively, than that of the C-terminal truncated enzyme. However, both recombinants showed similar hydrolysis patterns of hexa-N-acetyl-chitohexaose (soluble substrate), producing di-N-acetyl-chitobiose as major product on TLC analysis. We showed that the C-terminus of the V. proteolyticus chitinase A was important for expression of high specific activity against insoluble chitins.

Production of a recombinant chitin oligosaccharide deacetylase from Vibrio parahaemolyticus in the culture medium of Escherichia coli cells

An open reading frame (ORF) encoding chitin oligosaccharide deacetylase (Pa-COD) gene and its signal sequence was cloned from the Vibrio parahaemolyticus KN1699 genome and its sequence was analyzed. The ORF encoded a 427 amino acid protein, including the 22 amino acid signal sequence. The deduced amino acid sequence was highly similar to several bacterial chitin oligosaccharide deacetylases in carbohydrate esterase family 4. An expression plasmid containing the gene was constructed and inserted into Escherichia coli cells and the recombinant enzyme was secreted into the culture medium with the aid of the signal peptide. The concentration of the recombinant enzyme in the E. coli culture medium was 150 times larger than that of wild-type enzyme produced in the culture medium by V. parahaemolyticus KN1699. The recombinant enzyme was purified to homogeneity from culture supernatant in an overall yield of 16%. Substrate specificities of the wild-type and the recombinant enzymes were comparable.

Purification and characterization of Vibrio parahaemolyticus extracellular chitinase and chitin oligosaccharide deacetylase involved in the production of heterodisaccharide from chitin

A chitin-degrading bacterial strain, KN1699, isolated from Yatsu dry beach (Narashino, Chiba Prefecture, Japan), was identified as Vibrio parahaemolyticus. Treatment of powdered chitin with crude enzyme solution prepared from the supernatant of KN1699 cultures yielded a disaccharide, beta-D-N-acetylglucosaminyl-(1,4)-D-glucosamine (GlcNAc-GlcN), as the primary chitin degradation product. The extracellular enzymes involved in the production of this heterodisaccharide, chitinase (Pa-Chi; molecular mass, 92 kDa) and chitin oligosaccharide deacetylase (Pa-COD; molecular mass, 46 kDa), were isolated from the crude enzyme solution, and their hydrolysis specificities were elucidated. These studies confirmed that (1) Pa-Chi hydrolyzes chitin to produce (GlcNAc)(2) and (2) Pa-COD hydrolyzes the acetamide group of reducing end GlcNAc residue of (GlcNAc)(2). These findings indicate that GlcNAc-GlcN is produced from chitin by the cooperative hydrolytic reactions of both Pa-Chi and Pa-COD.

Suppressive effect of partially hydrolyzed guar gum on transitory diarrhea induced by ingestion of maltitol and lactitol in healthy humans

OBJECTIVES

To estimate the suppressive effect of partially hydrolyzed guar gum (PHGG) on transitory diarrhea induced by ingestion of a sufficient amount of maltitol or lactitol in female subjects.

DESIGN

The first, the minimal dose level of maltitol and lactitol that would induce transitory diarrhea was estimated separately for each subject. Individual subject was administered a dose that increased by 5 g stepwise from 10 to 45 g until diarrhea was experienced. Thereafter, the suppressive effect on diarrhea was observed after each subject ingested a mixture of 5 g of PHGG and the minimal dose level of maltitol or lactitol.

SETTING

Laboratory of Public Health Nutrition, Department of Nutrition and Health Sciences, Siebold University of Nagasaki.

SUBJECTS

Thirty-four normal female subjects (21.3+/-0.9 years; 49.5+/-5.3 kg).

MAIN OUTCOME MEASUREMENT

Incidence of diarrhea caused by the ingestion of maltitol or lactitol and the ratio of suppression achieved by adding PHGG for diarrhea.

RESULTS

The ingestion of amounts up to 45 g of maltitol, diarrhea caused in 29 of 34 subjects (85.3%), whereas the ingestion of lactitol caused diarrhea in 100%. The diarrhea owing to maltitol was improved in 10 of 28 subjects by the addition of 5 g of PHGG to minimal dose-induced diarrhea, and that owing to lactitol was in seven of 19 subjects. Adding 10 g of PHGG strongly suppressed the diarrhea caused by maltitol, and the cumulative ratio was 82.1% (23/28).

CONCLUSION

The transitory diarrhea caused by the ingestion of maltitol or lactitol was clearly suppressed by the addition of PHGG. These results strongly suggest that diarrhea caused by the ingestion of a sufficient amount of non-digestible sugar substitute can be suppressed by the addition of dietary fiber.

Crystal structure of oxidized cytochromec6AfromArabidopsis thaliana

Compared with algal and cyanobacterial cytochrome c(6), cytochrome c(6A) from higher plants contains an additional loop of 12 amino acid residues. We have determined the first crystal structure of cytochrome c(6A) from Arabidopsis thaliana at 1.5 Angstrom resolution in order to help elucidate its function. The overall structure of cytochrome c(6A) follows the topology of class I c-type cytochromes in which the heme prosthetic group covalently binds to Cys16 and Cys19, and the iron has octahedral coordination with His20 and Met60 as the axial ligands. Two cysteine residues (Cys67 and Cys73) within the characteristic 12 amino acids loop form a disulfide bond, contributing to the structural stability of cytochrome c(6A). Our model provides a chemical basis for the known low redox potential of cytochrome c(6A) which makes it an unsuitable electron carrier between cytochrome b(6)f and PSI.

Planar Catechin Analogues with Alkyl Side Chains: A Potent Antioxidant and an α-Glucosidase Inhibitor

Planar catechin analogues having various alkyl side chain lengths were synthesized, and their remarkable antioxidative abilities and alpha-glucosidase inhibitory activities are shown.

Result of neck clipping and coil embolization as a treatment for subarachnoid haemorrhage

SUMMARY

The report of the International Subarachnoid Aneurysm Trial (ISAT) study showed that coil embolization was superior to neck clipping as a treatment for subarachnoid haemorrhage (SAH) (1). We compared the results of coil embolization and neck clipping in our institute. Generally better outcomes were obtained by endovascular surgery than neck clipping. Symptomatic vasospasm and symptomatic hydrocephalus occurred less frequently in coil embolization than neck clipping. Because not all cases of SAH can be treated by coil embolization due to the width of aneurysmal neck and relation of the aneurysm to parent arteries, we should also be able to perform neck clipping as another modality.

Aglycon specificity profiling of α-glucosidases using synthetic probes

We designed and synthesized hydrogen bond based probes 1-8 with the exception of known glycosidase inhibition mechanisms, and aglycon specificity of 11 different sources of alpha-glucosidases were investigated using their probes. Probe 4 (2,6-anhydro-1-deoxy-1-[(1-oxopentyl-5-hydroxy)amino]-D-glycero-D-ido-heptitol) showed a potent inhibition of S. cerevisiae alpha-glucosidase among all alpha-glucosidases. Probe 4 was found to be a competitive inhibitor for S. cerevisiae alpha-glucosidase with Ki 0.13 mM.

Design and Synthesis of de Novo Cytochromes c

Natural c-type cytochromes are characterized by the consensus Cys-X-X-Cys-His heme-binding motif (where X is any amino acid) by which the heme is covalently attached to protein by the addition of the sulfhydryl groups of two cysteine residues to the vinyl groups of the heme. In this work, the consensus sequence was used for the heme-binding site of a designed four-helix bundle, and the apoproteins with either a histidine residue or a methionine residue positioned at the sixth coordination site were synthesized and reacted with iron protoporphyrin IX (protoheme) under mild reducing conditions in vitro. These polypeptides bound one heme per helix-loop-helix monomer via a single thioether bond and formed four-helix bundle dimers in the holo forms as designed. They exhibited visible absorption spectra characteristic of c-type cytochromes, in which the absorption bands shifted to lower wavelengths in comparison with the b-type heme binding intermediates of the same proteins. Unexpectedly, the designed cytochromes c with bis-His-coordinated heme iron exhibited oxidation-reduction potentials similar to those of their b-type intermediates, which have no thioether bond. Furthermore, the cytochrome c with His and Met residues as the axial ligands exhibited redox potentials increased by only 15-30 mV in comparison with the cytochrome with the bis-His coordination. These results indicate that highly positive redox potentials of natural cytochromes c are not only due to the heme covalent structure, including the Met ligation, but also due to noncovalent and hydrophobic environments surrounding the heme. The covalent attachment of heme to the polypeptide in natural cytochromes c may contribute to their higher redox potentials by reducing the thermodynamic stability of the oxidized forms relatively against that of the reduced forms without the loss of heme.

α-Mannosidase-catalyzed synthesis of a (1→2)-α-d-rhamnodisaccharide derivative

Enzymatic transglycosylation using p-nitrophenyl alpha-D-rhamnopyranoside as the glycosyl donor and 6equiv of ethyl 1-thio-alpha-D-rhamnopyranoside as the glycosyl acceptor yielded a D-rhamnooligosaccharide derivative. The reaction was catalyzed by jack bean alpha-mannosidase in a 1:1 (v/v) mixture of 0.1 M sodium citrate buffer (pH4.5)-MeCN at 25 degrees C. The enzyme exhibited high catalytic activity for the reaction, to afford in 32.1% isolated yield (based on donor substrate) ethyl alpha-D-rhamnopyranosyl-(1-->2)-1-thio-alpha-D-rhamnopyranoside, which is a derivative of the common oligosaccharide unit of the antigenic lipopolysaccharides from Pseudomonas.

A novel microperoxidase activity: methyl viologen-linked nitrite reducing activity of microperoxidase

To investigate the nitrite reducing activity of microperoxidases (mps) in the presence of methyl viologen and dithionite, the fragments C14-K22 (mp9), V11-L32 (mp22), and G1-M65 (mp65) containing heme were prepared by enzymatic hydrolysis of commercially equine heart cytochrome c (Cyt c), in which His is axially coordinated to heme iron, and acts as its fifth ligand. The nitrite reducing activity of mps was measured under anaerobic condition, and the nitrite reducing activity of mps increased with the cutting of the peptide chain. The activity of the shortest nonapeptide mp9 was approximately 120-fold that of Cyt c (104 amino acid residues) and 3.2-fold that of nitrite reductase (EC 1.7.7.1) from Escherichia coli. In the nitrite reduction by mp, nitrite was completely reduced to ammonia. We presumed that ferrous mps reduced NO2- to NO by donating one electron, the NO was completely reduced to NH4+ under anaerobic condition via ferrous-NO complexes as a reaction intermediate using visible spectra and ESR spectra, and this overall reaction was a 6-electron and 8-proton reduction. Sepharose-immobilized mp9 had a nitrite reducing activity similar to that of mp9 in solution, and the resin retained the activity after five uses and even 1-year storage. The mp will be able to use as a substitute for nitrite reductase.

Development of a Genetic System in Chitinase-Producing Streptomyces and the Application of an Allosamidin-Insensitive Chitinase Gene to Homologous Overexpression

A transformation system for Streptomyces sp. AJ9463 strain (allosamidin producer) was successfully developed using protoplasts and a PEG-mediated method. To prepare protoplasts, the concentration of glycine and sucrose in YEME medium were optimized to 0.5% (w/v) and 34.0% (w/v), respectively. When the protoplasts of Streptomyces sp. AJ9463 were transformed with pUWL-KS, transformants could be obtained at a high efficiency of 7.0 x 10(4) transformants per microg DNA. To ensure that the transformation system worked properly, we then constructed a constitutive expression vector pYK1, in which the ermE* promoter drives transcription of the allosamidin-insensitive chitinase gene, chiIS. Although no transformant could be obtained by the genetic system using pYK1 isolated from Escherichia coli DH5alpha, pYK1 isolated from the methylase-deficient mutant E. coli SCS110, could be introduced into Streptomyces sp. AJ9463. This indicates that Streptomyces sp. AJ9463 has a methylation-specific restriction system, and that the chiIS and/or ermE* promoter region of pYK1 includes a restriction site of its endonuclease. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) indicated that pYK1 in Streptomyces sp. AJ9463 started to obviously express ChiIS from 14-h. Moreover, the pYK1-introduced strain gave a five-fold higher chitinase activity than the wild-type, suggesting that this system can be widely applied for the overexpression and gene functional analysis.

Radiation-induced enhancement of nitrite reducing activity of cytochrome c

Commercial cytochrome c (Cyt c) was irradiated with Co-60 gamma-rays in the dose range of up to 3.0 kGy to investigate the enhancement of the nitrite reducing activity of Cyt c. The optimum irradiation dose to induce nitrite reducing activity for 30 muM Cyt c solution was 1.0 kGy under an O(2) atmosphere. The nitrite reducing activity of Cyt c irradiated at this dose was approximately 45-fold that of unirradiated Cyt c and ca. 1.2-fold that of nitrite reductase. The irradiation treatment resulted in unfolding of the peptide chain, exposure of the heme group, oxidation of methionine to methionine sulfoxide, dissociation of the sixth ligand (Met), and occurrence of autoxidation in Cyt c. Sepharose-immobilized irradiated Cyt c had a similar activity to that in solution. The resin retained the activity after five uses even after 1 year of storage. The irradiated Cyt c will be able to be used as a substitute for nitrite reductase.

Comparison of digestibility and breath hydrogen gas excretion of fructo-oligosaccharide, galactosyl-sucrose, and isomalto-oligosaccharide in healthy human subjects

OBJECTIVES

To clarify the difference of digestibility in the small intestine among fructo-oligosaccharide (FOS), galactosyl-sucrose (GS), and isomalto-oligosaccharide (IMO) using breath hydrogen test.

DESIGN

The first step: screening test of breath hydrogen excretion and FOS tolerance test to select the subjects. The second step: breath hydrogen test of three kinds of oligosaccharides, carried out using precautionary regulations. The ingestion order was 10 g of FOS, GS, and IMO, with increases, at 1-week interval, up to 20 g, respectively. Breath gas was collected before, at 20 min intervals from 40 to 120 min after, and at 30 min intervals from 120 min to 7 h after ingestion of test substance.

SETTING

Laboratory of Public Health Nutrition, Department of Nutrition and Health Sciences, Siebold University of Nagasaki, Nagasaki, Japan.

SUBJECTS

A total of nine males (average: age 25.7+/-3.5 y, weight 61.9+/-8.8 kg, height 170.0+/-6.0 cm) and 29 females (average: 23.1+/-7.2 y, 52.9+/-5.3 kg, 157.5+/-5.1 cm) from the University of Tokyo and Siebold University of Nagasaki.

MAIN OUTCOME MEASURES

Breath hydrogen excretion from end-expiratory gas.

RESULT

: Breath hydrogen of FOS was more remarkably excreted than that of GS; that of IMO was slight; and that of AUC (10 g) was significantly different. FOS was 9768+/-3253 ppm, GS was 3662+/-2632 ppm, and IMO was 831+/-1154 ppm. A dose dependence was observed at doses between 10 and 20 g of FOS and GS, and the initial time of 20 g was earlier than that of 10 g.

CONCLUSIONS

FOS was not hydrolyzed, GS was slightly hydrolyzed, and IMO was readily hydrolyzed by small intestinal enzymes. H(2) gas reflected fermentability in the large intestine.

SPONSORSHIP

Siebold University of Nagasaki.

Glycosidase-catalyzed deoxy oligosaccharide synthesis. Practical synthesis of monodeoxy analogs of ethyl beta-thioisomaltoside using Aspergillus niger alpha-glucosidase

Enzymatic transglycosylation using four possible monodeoxy analogs of p-nitrophenyl alpha-D-glucopyranoside (Glc alpha-O-pNP), modified at the C-2, C-3, C-4, and C-6 positions (2D-, 3D-, 4D-, and 6D-Glc alpha-O-pNP, respectively), as glycosyl donors and six equivalents of ethyl beta-D-thioglucopyranoside (Glc beta-S-Et) as a glycosyl acceptor, to yield the monodeoxy derivatives of glucooligosaccharides were done. The reaction was catalyzed using purified Aspergillus niger alpha-glucosidase in a mixture of 50 mM sodium acetate buffer (pH 4.0)/CH3CN (1:1 v/v) at 37 degrees C. High activity of the enzyme was observed in the reaction between 2D-Glc alpha-O-pNP and Glc beta-S-Et to afford the monodeoxy analogs of ethyl beta-thiomaltoside and ethyl beta-thioisomaltoside that contain a 2-deoxy alpha-D-glucopyranose moiety at their glycon portions, namely ethyl 2-deoxy-alpha-D-arabino-hexopyranosyl-(1,4)-beta-D-thioglucopyranoside and ethyl 2-deoxy-alpha-D-arabino-hexopyranosyl-(1,6)-beta-D-thioglucopyranoside, in 6.72% and 46.6% isolated yields (based on 2D-Glc alpha-O-pNP), respectively. Moreover, from 3D-Glc alpha-O-pNP and Glc beta-S-Et, the enzyme also catalyzed the synthesis of the 3-deoxy analog of ethyl beta-thioisomaltoside that was modified at the glycon alpha-D-glucopyranose moiety, namely ethyl 3-deoxy-alpha-D-ribo-hexopyranosyl-(1,6)-beta-D-thioglucopyranoside, in 23.0% isolated yield (based on 3D-Glc alpha-O-pNP). Products were not obtained from the enzymatic reactions between 4D- or 6D-Glc alpha-O-pNP and Glc beta-S-Et.