Indications and practice for tube feeding in Japanese geriatricians: implications of multidisciplinary team approach.

AIM: The aim of this study was to examine how geriatricians decide the indication of tube feeding in the elderly with eating difficulty as a result of several disorders, and to determine the factors associated with their decision making and interventions for dysphagia. METHODS: The design was a cross-sectional study. All board-certified geriatricians in the Japan Geriatrics Society were recruited to this study in September 2010. We sent questionnaires to 1469 geriatricians. Among them, 629 agreed to participate. The survey consisted of self-administered questionnaires regarding demographic information, indications of tube feeding and interventions for dysphagia before tube feeding. RESULTS: We analyzed the remaining 555 questionnaires after excluding incomplete ones. Over 90% of geriatricians answered that "neurological disorder" and "stroke" are indications, whereas 46.8% of them answered that "dementia" is an indication for tube feeding. Geriatricians who organize a multidisciplinary team conference tended to carry out more "interventions for dysphagia before the prescription of tube feeding" compared with the reference group (odds ratio 2.1-8.7) after multivariate adjustment. CONCLUSIONS: The results show that approximately half of the geriatricians prescribe tube feeding when the patient has dementia with loss of appetite or apraxia for eating. There is no consensus among Japanese geriatricians about the indication of tube feeding for demented people. We suggest that guidelines for tube feeding in the elderly should be established. Furthermore, a multidisciplinary approach would be desirable for decision making for tube feeding.

Structural basis for the Helicobacter pylori-carcinogenic TNF-alpha-inducing protein.

Stomach cancer is strongly associated with infection by Helicobacter pylori. In 2005, we identified a new H. pylori gene encoding a TNF-alpha inducing protein (Tipalpha) that acts as a carcinogenic factor. Tipalpha is secreted from H. pylori as a homodimer whose subunits are linked by disulfide bonds. We also characterized a Tipalpha deletion mutant (del-Tipalpha) that lacks the N-terminal six amino acid residues (LQACTC), including two cysteines (C5 and C7) that form disulfide bonds, but nonetheless shows a weak ability to induce TNF-alpha expression. Here we report that del-Tipalpha has a novel elongated structure containing a 40-A-long alpha helix, and forms a heart-shaped homodimer via non-covalent bonds. Moreover, their circular dichroism spectra strongly suggest that the structures of the del-Tipalpha and Tipalpha homodimers are very similar. del-Tipalpha's unique mode of dimer formation provides important insight into protein-protein interactions and into the mechanism underlying the carcinogenicity of H. pylori infection.

Structural basis for the kexin-like serine protease from Aeromonas sobria as sepsis-causing factor.

The anaerobic bacterium Aeromonas sobria is known to cause potentially lethal septic shock. We recently proposed that A. sobria serine protease (ASP) is a sepsis-related factor that induces vascular leakage, reductions in blood pressure via kinin release, and clotting via activation of prothrombin. ASP preferentially cleaves peptide bonds that follow dibasic amino acid residues, as do Kex2 (Saccharomyces cerevisiae serine protease) and furin, which are representative kexin family proteases. Here, we revealed the crystal structure of ASP at 1.65 A resolution using the multiple isomorphous replacement method with anomalous scattering. Although the overall structure of ASP resembles that of Kex2, it has a unique extra occluding region close to its active site. Moreover, we found that a nicked ASP variant is cleaved within the occluding region. Nicked ASP shows a greater ability to cleave small peptide substrates than the native enzyme. On the other hand, the cleavage pattern for prekallikrein differs from that of ASP, suggesting the occluding region is important for substrate recognition. The extra occluding region of ASP is unique and could serve as a useful target to facilitate development of novel antisepsis drugs.

Crystallization and X-ray diffraction analysis of the RNA primer/promoter-binding domain of influenza A virus RNA-dependent RNA polymerase PB2.

The C-terminal domain protein (amino-acid residues 535-759) of the PB2 subunit of the RNA-dependent RNA polymerase from the highly pathogenic influenza A virus was expressed as a soluble protein in Escherichia coli and crystallized using sodium formate as a precipitant. Data sets were collected from crystals of native and selenomethionine-substituted protein on the KEK NW12 beamline at the Photon Factory and the crystals diffracted to a maximum resolution of 2.44 A for the SeMet-derivative crystal. The native crystals were found to belong to space group P3(2)21, with unit-cell parameters a = b = 52.5, c = 156.3 A. The Matthews value (V(M)) was 2.7 A(3) Da(-1), assuming the presence of one molecule in the asymmetric unit. The SeMet-derivative crystals were found to belong to the same space group, with unit-cell parameters a = b = 52.6, c = 156.4 A. Attempts are being made to solve the structure by multi-wavelength anomalous dispersion phasing.

Structural basis of the influenza A virus RNA polymerase PB2 RNA-binding domain containing the pathogenicity-determinant lysine 627 residue.

Because the influenza A virus has an RNA genome, its RNA-dependent RNA polymerase, comprising the PA, PB1, and PB2 subunits, is essential for viral transcription and replication. The binding of RNA primers/promoters to the polymerases is an initiation step in viral transcription. In our current study, we reveal the 2.7 A tertiary structure of the C-terminal RNA-binding domain of PB2 by x-ray crystallography. This domain incorporates lysine 627 of PB2, and this residue is associated with the high pathogenicity and host range restriction of influenza A virus. We found from our current analyses that this lysine is located in a unique "phi"-shaped structure consisting of a helix and an encircled loop within the PB2 domain. By electrostatic analysis, we identified a highly basic groove along with this phi loop and found that lysine 627 is located in the phi loop. A PB2 domain mutant in which glutamic acid is substituted at position 627 shows significantly lower RNA binding activity. This is the first report to show a relationship between RNA binding activity and the pathogenicity-determinant lysine 627. Using the Matras program for protein three-dimensional structural comparisons, we further found that the helix bundles in the PB2 domain are similar to that of activator 1, the 40-kDa subunit of DNA replication clamp loader (replication factor C), which is also an RNA-binding protein. This suggests a functional and structural relationship between the RNA-binding mechanisms underlying both influenza A viral transcription and cellular DNA replication. Our present results thus provide important new information for developing novel drugs that target the primer/promoter RNA binding of viral RNA polymerases.

Structural basis of actin recognition and arginine ADP-ribosylation by Clostridium perfringens iota-toxin.

The ADP-ribosylating toxins (ADPRTs) produced by pathogenic bacteria modify intracellular protein and affect eukaryotic cell function. Actin-specific ADPRTs (including Clostridium perfringens iota-toxin and Clostridium botulinum C2 toxin) ADP-ribosylate G-actin at Arg-177, leading to disorganization of the cytoskeleton and cell death. Although the structures of many actin-specific ADPRTs are available, the mechanisms underlying actin recognition and selective ADP-ribosylation of Arg-177 remain unknown. Here we report the crystal structure of actin-Ia in complex with the nonhydrolyzable NAD analog betaTAD at 2.8 A resolution. The structure indicates that Ia recognizes actin via five loops around NAD: loop I (Tyr-60-Tyr-62 in the N domain), loop II (active-site loop), loop III, loop IV (PN loop), and loop V (ADP-ribosylating turn-turn loop). We used site-directed mutagenesis to confirm that loop I on the N domain and loop II are essential for the ADP-ribosyltransferase activity. Furthermore, we revealed that Glu-378 on the EXE loop is in close proximity to Arg-177 in actin, and we proposed that the ADP-ribosylation of Arg-177 proceeds by an SN1 reaction via first an oxocarbenium ion intermediate and second a cationic intermediate by alleviating the strained conformation of the first oxocarbenium ion. Our results suggest a common reaction mechanism for ADPRTs. Moreover, the structure might be of use in rational drug design to block toxin-substrate recognition.

Extracellular matrix remodeling in oral submucous fibrosis: its stage-specific modes revealed by immunohistochemistry and in situ hybridization.

BACKGROUND: Oral submucous fibrosis (OSF) is a chewing habit-related pre-cancerous condition of the oral mucosa affecting predominantly south Asians. It is histopathologically characterized by epithelial atrophy and fibrosis of the subepithelial connective tissue. Fibrosis extends all the way into the muscle layer, leading to difficulty in mouth opening. However, the dynamics of extracellular matrix (ECM) remodeling with OSF progression is largely unknown. METHODS: Forty biopsy specimens of OSF and 10 of normal buccal mucosa were examined for expression/deposition modes of eight ECM molecules by histochemistry, immunohistochemistry, and in situ hybridization. RESULTS: In the early stage of OSF, tenascin, perlecan, fibronectin, collagen type III were characteristically enhanced in the lamina propria and the submucosal layer. In the intermediate stage, the ECM molecules mentioned above and elastin were extensively and irregularly deposited around muscle fibers. In the advanced stage, such ECM depositions decreased and were entirely replaced with collagen type I only. Their gene expression levels varied with progression of fibrosis, but the mRNA signals were confirmed in fibroblasts in the submucosal fibrotic areas. CONCLUSIONS: The results indicate that the ECM remodeling steps in OSF are similar to each phase of usual granulation tissue formation. Restricted mouth opening may be a result of loss of variety of ECM molecules including elastin into the homogeneity of collagen type I replacing muscle fibers.

A 17-year follow-up study of hypertensive and normotensive male university students in Japan.

The aim of the present study was to determine the disease course of hypertensive male university students followed for 8 to 26 years (average, 17 years) after graduation. Subjects were classified into two groups. 1) A hypertensive group (H-group) consisting of 338 conclusively hypertensive male students followed from 1973 to 1990 at the Institute of Health Science, Kyushu University. Their ages ranged from 20 to 27 years, and all had high blood pressure (BP) of 140 mmHg or greater in systole (SBP) and/or 90 mmHg or greater in diastole (DBP) at a regular health check. This was confirmed by BP measurements for 3 days within 1 week. 2) A normotensive control group (N-group) consisting of 732 normotensive students (110-124 SBP/60-74mmHg DBP) for whom faculty, age, sex, height, weight, and examination period were matched to the H-group as closely as possible. In 1997, each subject was sent a questionnaire with items on height, weight, sitting BP, pulse rate, family history of hypertension, lifestyle habits (such as drinking and smoking), stress and personality type. Completing the questionnaire were 177 (52.4%) of the H-group and 206 (28.1%) of the N-group subjects. Hypertension continued in 44.6% of the H-group subjects, whereas 9.2% of the N-group subjects became hypertensive. The rate of hypertension at the end of the investigation was significantly higher in those subjects who had a family history of hypertension than in those who did not. Weight gain (+15.1%) was the highest in H-group subjects who were initially normotensive. These subjects showed a significantly higher incidence of smoking and drinking than the other subjects. These results confirmed lifestyle to be one of the most important factors in keeping BP normal throughout life and also suggested that fundamental health education should be introduced at an early age.

Activation of protein kinase C inhibits the secretion of platelet-activating factor acetylhydrolase by human decidual macrophages.

Background and Aims: Platelet activating factor (PAF), a potent phospholipid mediator, has been implicated in a number of reproductive processes through ovulation to parturition. To clarify the regulatory mechanism of PAF metabolism in the decidua, we have investigated the effect of activation of protein kinase C (PKC) on the secretion of PAF-acetylhydrolase (PAF-AH), a PAF-inactivating enzyme, by human decidual macrophages. Methods: Decidual macrophage populations were isolated from human decidua by using enzymic digestion, Ficoll-Paque centrifugation, or flow cytometric sorting. The cells were treated with a PKC activator (TPA), H-7, dibutyryl cyclic adenosine monophosphate (AMP), Bis-(o-aminophenoxy)-ethane-N,N,N',N'-tetraacetic acid, tetra (acetoxymethyl)-ester (BAPTA/AM) and/or nifedipine. The activity of PAF-AH secreted in the culture medium was assayed. Results: The PKC activator, TPA, inhibited the PAF-AH secretion by decidual cells in a dose-dependent manner. The TPA also decreased the enzyme secretion by flow cytometrically purified macrophages. The inhibitory effect of TPA was blocked by a PKC inhibitor, H-7. Protein kinase A (PKA) activation by dibutyryl cyclic AMP was without effect on the enzyme secretion. Calcium channel blockers, BAPTA/AM and nifedipine had no effect on the PAF-AH secretion. Conclusion: It is suggested that the TPA-induced inhibition of PAF-AH secretion may be mediated, in part, by a PKC-dependent signal transduction, and that activation of PKC may result in the increase in the local concentration of PAF in the decidua because of its inhibitory effect on the PAF-AH secretion by decidual macrophages. (Reprod Med Biol 2003; 2: 121-126).