SWI by 7T MR Imaging for the Microscopic Imaging Diagnosis of Astrocytic and Oligodendroglial Tumors.

BACKGROUND AND PURPOSE: Despite advances in molecular imaging, preoperative diagnosis of astrocytomas and oligodendrogliomas can be challenging. In the present study, we assessed whether 7T SWI can be used to distinguish astrocytomas and oligodendrogliomas and whether malignant grading of gliomas is possible. MATERIALS AND METHODS: 7T SWI was performed on 21 patients with gliomas before surgery with optimization for sharp visualization of the corticomedullary junction. Scoring for cortical thickening and displacement of medullary vessels, characteristic of oligodendroglial tumors, and cortical tapering, characteristic of astrocytic tumors, was performed. Additionally, characteristics of malignancy, including thickening of the medullary veins, the presence of microbleeds, and/or necrosis were scored. RESULTS: Scoring for oligodendroglial (highest possible score, +3) and astrocytic (lowest score possible, -3) characteristics yielded a significant difference between astrocytomas and oligodendrogliomas (mean, -1.93 versus +1.71, P < .01). Scoring for malignancy was significantly different among the World Health Organization grade II (n = 10), grade III (n = 4), and grade IV (n = 7) tumors (mean, 0.20 versus 1.38 versus 2.79). Cortical thickening was observed significantly more frequently in oligodendrogliomas (P < .02), with a sensitivity of 71.4% and specificity of 85.7%; observation of tapering of the cortex was higher in astrocytomas (P < .01) with a sensitivity of 85.7% and specificity of 100%. CONCLUSIONS: Visualization of the corticomedullary junction by 7T SWI was useful in distinguishing astrocytomas and oligodendrogliomas. Observation of tapering of the cortex was most sensitive and specific for diagnosing astrocytomas. Reliably predicting malignant grade was also possible by 7T SWI.

Development of retake support system for lateral knee radiographs by using deep convolutional neural network.

INTRODUCTION: Lateral radiography of the knee joint is frequently performed; however, the retake rate is high owing to positioning errors. Therefore, in this study, to reduce the required number and time of image retakes, we developed a system that can classify the tilting directions of lateral knee radiographs and evaluated the accuracy of the proposed method. METHODS: Using our system, the tilting directions of a lateral knee radiographs were classified into four direction categories. The system was developed by training the DCNN based on 50 cases of Raysum images and tested on three types test dataset; ten more cases of Raysum images, one case of flexed knee joint phantom images and 14 rejected knee joint radiographs. To train a deep convolutional neural network (DCNN), we employed Raysum images created via three-dimensional (3D) X-ray computed tomography (CT); 11 520 Raysum images were created from 60 cases of 3D CT data by changing the projection angles. Thereby, we obtained pseudo images attached with correct labels that are essential for training. RESULTS: The overall accuracy on each test dataset was 88.5 ± 7.0% (mean ± standard deviation), 81.4 ± 11.2%, and 73.3 ± 9.2%. The larger the tilting degree of the knee joint, the higher the classification accuracy. CONCLUSION: DCNN could classify the tilting directions of a knee joint from lateral knee radiographs. Using Raysum images made it possible to facilitate creating dataset for training DCNN. The possibility was indicated for using support system of lateral knee radiographs. IMPLICATIONS FOR PRACTICE: The system may also reduce the burden on patients and increase the work efficiency of radiological technologists.

Collaboration of local government and experts responding to increase in environmental radiation level due to the nuclear disaster: focusing on their activities and latest radiological discussion.

Activities were introduced in Kashiwa city in the Tokyo metropolitan area to correspond to the elevated environmental radiation level after the disaster of the Fukushima Daiichi nuclear power plant. These were based on a strong cooperation between local governments and experts. Ambient dose rate and radioactivity of foodstuff produced inside of the city have been monitored. Representative ambient dose rates around living environments have almost already become their original levels of the pre-accident because of the decontamination activity, natural washout and effective half-lives of radioactivity. The internal annual dose due to radioactive cesium under the policy of 'Local Production for Local Consumption' is estimated as extremely low comparing the variation range due to natural radioactivity. Systematic survey around a retention basin has been started. All of these latest monitoring data would be one of the core information for the policy making as well as a cost-benefit discussion and risk communication.

Role of a highly conserved YPITP motif in 2-oxoacid:ferredoxin oxidoreductase: heterologous expression of the gene from Sulfolobus sp.strain 7, and characterization of the recombinant and variant enzymes.

2-Oxoacid:ferredoxin oxidoreductase from Sulfolobus sp. strain 7, an aerobic and thermoacidophilic crenoarchaeon, catalyses the coenzyme A-dependent oxidative decarboxylation of pyruvate and 2-oxoglutarate, a cognate Zn-7Fe-ferredoxin serving as an electron acceptor. It comprises two subunits, a (632 amino acids) and b (305 amino acids). To further elucidate its structure and function, we constructed a gene expression system. The wild-type recombinant enzyme was indistinguishable from the natural one in every criterion investigated. A series of variants was constructed to elucidate the role of the YPITP-motif (residues 253-257) in subunit a, which is conserved universally in the 2-oxoacid:ferredoxin oxidoreductase (OFOR) family. Single amino-acid replacements at Y253 and P257 by other amino acids caused a drastic loss of enzyme activity. T256, the hydroxyl group of which has been proposed to be essential for binding of the 2-oxo group of the substrate in the Desulfovibrio africanus enzyme, was unexpectedly replaceable with Ala, the kcat and Km for 2-oxoglutarate being approximately 33% and approximately 51%, respectively, as compared with that of the wild-type enzyme. Replacement at other positions resulted in a significant decrease in the kcat of the reaction while the Km for 2-oxoacid was only slightly affected. Thus, the YPITP-motif is essential for the turnover of the reaction rather than the affinity toward 2-oxoacid.

Identification of the catalytic residue of Thermococcus litoralis 4-alpha-glucanotransferase through mechanism-based labeling.

Thermococcus litoralis 4-alpha-glucanotransferase (TLGT) belongs to family 57 of glycoside hydrolases and catalyzes the disproportionation and cycloamylose synthesis reactions. Family 57 glycoside hydrolases have not been well investigated, and even the catalytic mechanism involving the active site residues has not been studied. Using 3-ketobutylidene-beta-2-chloro-4-nitrophenyl maltopentaoside (3KBG5CNP) as a donor and glucose as an acceptor, we showed that the disproportionation reaction of TLGT involves a ping-pong bi-bi mechanism. On the basis of this reaction mechanism, the glycosyl-enzyme intermediate, in which a donor substrate was covalently bound to the catalytic nucleophile, was trapped by treating the enzyme with 3KBG5CNP in the absence of an acceptor and was detected by matrix-assisted laser desorption ionization time-of-flight mass spectrometry after peptic digestion. Postsource decay analysis suggested that either Glu-123 or Glu-129 was the catalytic nucleophile of TLGT. Glu-123 was completely conserved between family 57 enzymes, and the catalytic activity of the E123Q mutant enzyme was greatly decreased. On the other hand, Glu-129 was a variable residue, and the catalytic activity of the E129Q mutant enzyme was not decreased. These results indicate that Glu-123 is the catalytic nucleophile of TLGT. Sequence alignment of TLGT and family 38 enzymes (class II alpha-mannosidases) revealed that Glu-123 of TLGT corresponds to the nucleophilic aspartic acid residue of family 38 glycoside hydrolases, suggesting that family 57 and 38 glycoside hydrolases may have had a common ancestor.

Efficient lentiviral transduction of human cord blood CD34(+) cells followed by their expansion and differentiation into dendritic cells.

OBJECTIVE: To support immune reconstitution after cord blood transplantation, immunotherapy using gene-modified dendritic cells (DCs), the most potent antigen-presenting cells, can be a powerful strategy for preventing infection and recurrence. To investigate the applicability of lentiviral vector-transduced DCs compared to retroviral vectors, we transduced umbilical cord blood (CB) CD34(+) cells, then expanded and differentiated them into DCs. MATERIALS AND METHODS: We transduced CB CD34(+) cells by vesicular stomatitis virus G-protein pseudotyped self-inactivating lentiviral vector or retroviral vectors carrying the enhanced green fluorescent protein gene. The cells were expanded in the stroma-dependent culture system and transferred to the culture condition for developing DCs. The efficiency of transduction and expression of the transgene in severe combined immunodeficiency (SCID) mice-repopulating cells (SRCs) and DCs were compared between lentiviral vector and retroviral vectors. Induced DCs were cocultured with allogeneic or autologous T cells to test the ability to present antigens. RESULTS: CB CD34(+) cells transduced by lentiviral vector and expanded ex vivo sustained stable transgene expression and multipotentiality by assessing SRCs assay and clonogenic assay of bone marrow cells from the transplanted mice. DCs derived from these cells expressed green fluorescent protein and surface markers CD1a, CD80, and HLA-DR and showed potent allo-stimulatory activity as well as nontransduced DCs did. On the other hand, we did not detect transgene expression in SRCs and DCs transduced by retroviral vectors. CONCLUSION: Gene-modified DCs derived from ex vivo expanded CB CD34(+) cells transduced by lentiviral vector will be useful in future immunotherapy protocols.

HscA is involved in the dynamics of FtsZ-ring formation in Escherichia coli K12.

BACKGROUND: FtsZ, a homologue of eukaryotic tubulin, localizes throughout the cytoplasm in non-dividing Escherichia coli. However, it assembles in cytokinetic rings at the early stages of septation. Factors controlling the dynamics of FtsZ ring formation are unknown, and the molecular mechanism governing these dynamics is yet to be determined. RESULTS: At 42 degrees C, JE10715 mutant bacteria formed multinucleated filaments with a highly reduced number of FtsZ-rings at potential division sites. The JE10715 phenotype resulted from a mis-sense mutation in the hscA gene which encodes a heat shock Hsp70 family protein, with a single alanine-to-valine substitution at position 192 within the ATPase domain. Both JE10715 and the hscA knockout strain of JE10715 were completely complemented by a plasmid-born, wild-type hscA gene, but not by a mutant-type hscA715 gene. An hscA conditional knockout of the wild-type strain under non-permissive conditions exhibited longer rod cells with an abnormal localization of FtsZ. The over-expression of dnaK partially complemented the JE10715 mutation. In vitro, the ATPase activity of the mutant protein HscA715 was reduced to 63% of wild-type HscA activity. HscA co-sedimented with FtsZ-polymers in the presence of GTP. CONCLUSION: HscA is involved in FtsZ-ring formation, through a chaperon-like interaction with FtsZ. Defects in hscA, however, can partially be compensated for by redundant genes, including the wild-type dnaK.

Acute lethal injury of lung and liver in mice transplanted with ex vivo-expanded CTLs.

Clinical application of cytotoxic T lymphocytes (CTL) induced in vitro is extensively used for the treatment of viral infection and malignant diseases. We produced anti H-2d CTL in vitro from C57BL/6 (B6) splenocytes presensitized with (B6 x DBA/2) F1 (BDF1) splenocytes to establish a model system of CTL therapy. The specificity and cytotoxic activity were high enough (E/T ratio 1:1 = 38.8%) to induce graft versus host reaction. Though the total number of B6 splenocytes decreased by 0.27 during the 4 days of culture, the number of CD8+ lymphocytes increased 1.3-fold. When more than 5 x 10(6) cells of H-2d-reactive CTL were transplanted into BDF1 mice, mice died within 2 days postinduction. This lethal effect was not seen in the mice induced with ConA-stimulated T cells. Histological examination of the lungs and liver revealed massive infiltration of neutrophils in alveoli and the necrosis of hepatocytes. Therefore, this protocol was shown to be effective to produce alloantigen-specific CTLs and applicable to in vitro manipulation such as retrovirus-mediated gene transfer.

Three-dimensional anisotropy contrast magnetic resonance axonography to predict the prognosis for motor function in patients suffering from stroke.

OBJECT: The purpose of this study was to assess how early wallerian degeneration in the corticospinal tracts of patients who had suffered from stroke was detected using three-dimensional anisotropy contrast (3D-AC) magnetic resonance (MR) axonography and to explore the possibility of predicting the prognosis for motor function in these patients. METHODS: Ten healthy volunteers and 16 stroke patients with hemiparesis were studied using MR images including 3D-AC MR axonography images obtained using a 1.5-tesla MR imaging system. The axonography was performed using an echoplanar imaging method. All patients underwent MR studies 2, 3, and 10 weeks after stroke onset. To detect wallerian degeneration, the diffusion anisotropy in the corticospinal tracts at the level of the upper pons was evaluated on axial images. These MR findings were compared with the patients' motor functions, which were classified according to the Brunnstrom criteria 12 weeks after the onset of stroke. In all patients with poor recovery (Brunnstrom Stages I-IV), wallerian degeneration, which was demonstrated as a reduction in diffusion anisotropy on axonography images, could be observed in the corticospinal tracts; this degeneration was not found in patients with good recovery (Stages V and VI). Axonography could be used to detect degeneration between 2 and 3 weeks after stroke onset. On conventional T2-weighted MR images, hyperintense areas indicating wallerian degeneration were not detected until 10 weeks after stroke onset. CONCLUSIONS: With the aid of 3D-AC MR axonography, wallerian degeneration can be detected in the corticospinal tracts during the early stage of stroke (2-3 weeks after onset), much earlier than it can be detected using T2-weighted MR imaging. The procedure of 3D-AC MR axonography may be useful in predicting motor function prognosis in stroke patients.

Structural basis for the ADP-specificity of a novel glucokinase from a hyperthermophilic archaeon.

BACKGROUND: ATP is the most common phosphoryl group donor for kinases. However, certain hyperthermophilic archaea such as Thermococcus litoralis and Pyrococcus furiosus utilize unusual ADP-dependent glucokinases and phosphofructokinases in their glycolytic pathways. These ADP-dependent kinases are homologous to each other but show no sequence similarity to any of the hitherto known ATP-dependent enzymes. RESULTS: We solved the crystal structure at 2.3 A resolution of an ADP-dependent glucokinase from T. litoralis (tlGK) complexed with ADP. The overall structure can be divided into large and small alpha/beta domains, and the ADP molecule is buried in a shallow pocket in the large domain. Unexpectedly, the structure was similar to those of two ATP-dependent kinases, ribokinase and adenosine kinase. Comparison based on three-dimensional structure revealed that several motifs important both in structure and function are conserved, and the recognition of the alpha- and beta-phosphate of the ADP in the tlGK was almost identical with the recognition of the beta- and gamma-phosphate of ATP in these ATP-dependent kinases. CONCLUSIONS: Noticeable points of our study are the first structure of ADP-dependent kinase, the structural similarity to members of the ATP-dependent ribokinase family, its rare nucleotide specificity caused by a shift in nucleotide binding position by one phosphate unit, and identification of the residues that discriminate ADP- and ATP-dependence. The strict conservation of the binding site for the terminal and adjacent phosphate moieties suggests a common ancestral origin of both the ATP- and ADP-dependent kinases.

Enhancement of human cord blood CD34+ cell-derived NK cell cytotoxicity by dendritic cells.

NK cells and dendritic cells (DCs) are both important in the innate host defense. However, the role of DCs in NK cell-mediated cytotoxicity is unclear. In this study, we designed two culture systems in which human cord blood CD34(+) cells from the same donor were induced to generate NK cells and DCs, respectively. Coculture of the NK cells with DCs resulted in significant enhancement of NK cell cytotoxicity and IFN-gamma production. However, NK cell cytotoxicity and IFN-gamma production were not increased when NK cells and DCs were grown together separated by a transwell membrane. Functional studies demonstrated that 1) concanamycin A, a selective inhibitor of perforin/granzyme B-based cytolysis, blocked DC-stimulated NK cytotoxicity against K562 cells; and 2) neutralizing mAb against Fas ligand (FasL) significantly reduced DC-stimulated NK cytotoxicity against Fas-positive Jurkat cells. In addition, a marked increase of FasL mRNA and FasL protein expression was observed in DC-stimulated NK cells. The addition of neutralizing mAb against IL-18 and IL-12 significantly suppressed DC-stimulated NK cell cytotoxicity. Neutralizing IFN-gamma Ab almost completely inhibited NK cell cytotoxicity against Jurkat cells. These observations suggest that DCs enhance NK cell cytotoxicity by up-regulating both perforin/granzyme B- and FasL/Fas-based pathways. Direct interaction between DCs and NK cells is necessary for DC-mediated enhancement of NK cell cytotoxicity. Furthermore, DC-derived IL-18 and IL-12 were involved in the up-regulation of NK cell cytotoxicity, and endogenous IFN-gamma production plays an important role in Fas-mediated cytotoxicity.

Some Lactobacillus L-lactate dehydrogenases exhibit comparable catalytic activities for pyruvate and oxaloacetate.

The nonallosteric and allosteric L-lactate dehydrogenases of Lactobacillus pentosus and L. casei, respectively, exhibited broad substrate specificities, giving virtually the same maximal reaction velocity and substrate K(m) values for pyruvate and oxaloacetate. Replacement of Pro101 with Asn reduced the activity of the L. pentosus enzyme toward these alternative substrates to a greater extent than the activity toward pyruvate.

Folding pathway mediated by an intramolecular chaperone: the structural and functional characterization of the aqualysin I propeptide.

Aqualysin I, a thermostable homologue of subtilisin, requires its propeptide (ProA) to function as an intramolecular chaperone (IMC). To decipher the mechanisms through which propeptides can initiate protein folding, we characterized ProA in terms of its sequence, structure and function. Our results show that, in contrast to ProS (propeptide of subtilisin), ProA can fold spontaneously, reversibly and cooperatively into a stable monomeric alpha-beta conformation, even when isolated from its cognate protease-domain. ProA displays an indiscernible amount of tertiary structure with a considerable solvent-accessible hydrophobic surface, but is not a classical molten-globule folding intermediate. Moreover, despite showing only 21 % sequence identity with ProS, ProA can not only inhibit enzymatic activity with a magnitude tenfold greater than ProS, but can also chaperone subtilisin folding, albeit with a lower efficiency. The structure of ProA complexed with subtilisin is different from that of isolated ProA. Hence, additional interactions seem necessary to induce ProA into a compact structure. Our results also suggest that: (a) propeptides that are potent inhibitors are not necessarily better IMCs; (b) propeptides within the subtilase family appear polymorphic and; (c) the intrinsic instability within propeptides may be necessary for rapid activation of the cognate protein.

Requirement for the COOH-terminal pro-sequence in the translocation of aqualysin I across the cytoplasmic membrane in Escherichia coli.

Aqualysin I from Thermus aquaticus YT-1 is an extracellular subtilisin-type serine protease. The protease is synthesized as a distinct precursor composed of four functional domains: an N-terminal signal sequence, an N-terminal pro-sequence, a protease domain, and a C-terminal pro-sequence. The N-terminal pro-sequence is essential for the production of active aqualysin I while the C-terminal pro-sequence is required for extracellular secretion of aqualysin I. In an E. coli expression system, the function of C-terminal pro-sequence in the translocation of aqualysin I across the cytoplasmic membrane was investigated. More than 60-70% of the total activity was detected in the cytoplasmic fraction in the deletion mutations of the C-terminal pro-sequence while less than 30% was found in this fraction in wild type. In addition, in vitro processing of aqualysin I precursors with these mutations to a mature form promptly occurred and the folding into active aqualysin I was rapid. These results suggest that the C-terminal pro-sequence, probably in conjunction with the signal sequence, facilitates the translocation of the precursor across the cytoplasmic membrane by preventing the precursor from taking on an active conformation.

Application of a metal switch to aqualysin I, a subtilisin-type bacterial serine protease, to the S3 site residues, ser102 and gly131.

We applied 'metal switch' experiments to the S3 site residues, Ser102 and Gly131, of aqualysin I, a subtilisin-type serine protease. We showed that two histidines introduced at these positions did take part in histidine-metal-histidine bridge formation, and metal ions inhibited the protease activities. These results indicate that two histidines are near each other, and both side chains are metal-accessible. This is the first report on application of the metal-switch technique to a subtilisin-related enzyme.

Independent component-cross correlation-sequential epoch (ICS) analysis of high field fMRI time series: direct visualization of dual representation of the primary motor cortex in human.

A new technique for functional magnetic resonance imaging (fMRI) time series analysis is presented. The technique referred to here as independent component-cross correlation-sequential epoch (ICS) analysis is a hybrid technique of two standard methodologies of biological signal analysis, namely, data driven methods, represented by independent component analysis, and hypothesis driven methods, represented by a general linear model. The technique successfully identified four functionally discrete areas within the primary sensorimotor cortex (SMI) in normal human subjects based on blood oxygenation level dependent (BOLD) contrast functional magnetic resonance imaging (fMRI) time series performed on a high field (3.0 T) system. Each of the four areas identified corresponded to the four physiological subdivisions of SMI, recognized in primates to be essential for voluntary hand motion, namely, 4 anterior (MI-4a) and 4 posterior (MI-4p) of the primary motor cortex, and 3a and the 'classical' (Brodmann areas 1, 2, and 3b) primary sensory cortex, respectively. ICS analysis appears to be a highly reliable and versatile technique for fMRI time series analysis.

Extensive generation of human cord blood CD34(+) stem cells from Lin(-)CD34(-) cells in a long-term in vitro system.

Human CD34(-) hematopoietic stem cells (HSCs) have been identified as potential precursors of CD34(+) HSCs by using xenogeneic transplantation systems. However, the properties of CD34(+) cells generated from CD34(-) cells have not been precisely analyzed due to the lack of an in vitro system in which CD34(+) cells are continuously produced from CD34(-) cells. We conducted this study to determine whether CD34(+) cells generated in vitro from CD34(-) cells have long-term multilineage reconstitution abilities. Lin(-)CD34(-) population isolated from human cord blood was cultured in the presence of murine bone marrow stroma cell line, HESS-5, and human cytokines, thrombopoietin, Flk2/Flt3 ligand, stem cell factor, granulocyte colony-stimulating factor, interleukin 3 (IL-3), and IL-6. They were analyzed weekly for their surface markers expressions, colony-forming cells, long-term culture initiating cells (LTC-IC), and SCID repopulating cells (SRC) abilities up to 30 days of culture. In this culture system, more than 10(7) CD34(+) cells can be continuously generated from 10(4) CD34(-) cells over 30 days. These CD34(+) cells produce colony-forming units, LTC-IC, and SRC with multi-lineage differentiation, all of which are characteristic features of hematopoietic stem/progenitor cells. These findings suggest that CD34(-) HSCs have extensive potential for the generation of CD34(+) HSCs in vitro. This system provides a novel and potentially useful procedure to generate CD34(+) cells for clinical transplantation and gene therapy.

Asymmetric Samarium-Reformatsky Reaction of Chiral alpha-Bromoacetyl-2-oxazolidinones with Aldehydes.

The samarium(II) iodide mediated asymmetric Reformatsky-type reaction of chiral 3-bromoacetyl-2-oxazolidinones with various aldehydes was studied. A series of chiral 4-substituted 2-oxazolidinones 1-3 and 5,5-disubstituted "SuperQuat" oxazolidinones 4-5 were employed as chiral auxiliaries of the alpha-bromoacetic acid. The reaction of 1 with various aldehydes gave the alpha-unbranched beta-hydroxy carboximides in good yields with high diastereomeric excess values (up to >99% de). The majority of the reaction product derived from 5,5-diphenyl SuperQuat 5 were highly crystallinity; a single recrystallization yielding a diastereomerically pure product with the other diastereomer not detectable by spectroscopic methods. The absolute configurations of the beta-hydroxy carboximides were determined by signs of optical rotations of the corresponding known ethyl esters referring to the literature values. Hydrolytic cleavage of the appended of beta-hydroxy moieties from the auxiliary SuperQuats was readily achieved under mild conditions using lithium hydroxide; the corresponding carboxylic acids and the returned SuperQuats were obtained in good yields without any evidence of racemization. The first step of the reaction is the reduction of the alpha-bromo group to produce the samarium enolate, which adds to an aldehyde. The absolute configuration of the adduct (7i) derive from benzaldehyde was found to be R, with the samarium enolate favoring the transition state predicted from chelation control of the reagent; this is in analogy to the discussion that has been used for the corresponding titanium enolate. The stereochemistry of the reaction may be explained by incorporating the Nerz-Stormes-Thornton chair transition structure model.

Engineering subtilisin E for enhanced stability and activity in polar organic solvents.

We examined the effect of a novel disulfide bond engineered in subtilisin E from Bacillus subtilis based on the structure of a thermophilic subtilisin-type serine protease aqualysin I. Four sites (Ser163/Ser194, Lys170/Ser194, Lys170/Glu195, and Pro172/Glu195) in subtilisin E were chosen as candidates for Cys substitutions by site-directed mutagenesis. The Cys170/Cys195 mutant subtilisin formed a disulfide bond in B. subtilis, and showed a 5-10-fold increase in specific activity for an authentic peptide substrate for subtilisin, N-succinyl-L-Ala-L-Ala-L-Pro-L-Phe-p-nitroanilide, compared with the single-Cys mutants. However, the disulfide mutant had a 50% decrease in catalytic efficiency due to a smaller k(cat) and was thermolabile relative to the wild-type enzyme, whereas it was greatly stabilized relative to its reduced form. These results suggest that an electrostatic interaction between Lys170 and Glu195 is important for catalysis and stability in subtilisin E. Interestingly, the disulfide mutant was found to be more stable in polar organic solvents, such as dimethylformamide and ethanol, than the wild-type enzyme, even under reducing conditions; this is probably due to the substitution of uncharged Cys by charged surface residues (Lys170 and Glu195). Further, the amino-terminal engineered disulfide bond (Gly61Cys/Ser98Cys) and the mutation Ile31Leu were introduced to enhance the stability and catalytic activity. A prominent 3-4-fold increase in the catalytic efficiency occurred in the quintet mutant enzyme over the range of dimethylformamide concentration (up to 40%).

Inhibitory effects of bovine lactoferrin on the adherence of enterotoxigenic Escherichia coli to host cells.

Adherence is an essential and prerequisite step for the colonization of mucosal surfaces by enterotoxigenic Escherichia coli (ETEC). We studied the effect of bovine lactoferrin (BLF) on the adherence of ETEC to human epithelial cells in vitro, and to intestinal mucosa of ICR germfree mice in vivo. In the in vitro study, BLF was found to inhibit the adherence of ETEC. This adhesion-inhibiting activity of BLF was found to lessen with decreasing BLF concentration, but the data obtained suggest a positive inhibitory effect of BLF against the adhesion of ETEC cells. In the in vivo study, the counts of adherent bacteria in various sections of the intestinal tract (duodenum, jejunoileum, and large intestine) were lower in the BLF group than in the control group, suggesting the possible action of BLF as an intestinal tract adherence-blocking agent with regards to ETEC.