Critical roles of interactions among switch I-preceding residues and between switch II and its neighboring alpha-helix in conformational dynamics of the GTP-bound Ras family small GTPases

GTP-bound forms of Ras family small GTPases exhibit dynamic equilibrium between two interconverting conformations, "inactive" state 1 and "active" state 2. A great variation exists in their state distribution; H-Ras mainly adopts state 2, whereas M-Ras predominantly adopts state 1. Our previous studies based on comparison of crystal structures representing state 1 and state 2 revealed the importance of the hydrogen-bonding interactions of two flexible effector-interacting regions, switch I and switch II, with the γ-phosphate of GTP in establishing state 2 conformation. However, failure to obtain both state structures from a single protein hampered further analysis of state transition mechanisms. Here, we succeed in solving two crystal structures corresponding to state 1 and state 2 from a single Ras polypeptide, M-RasD41E, carrying an H-Ras-type substitution in residue 41, immediately preceding switch I, in complex with guanosine 5'-(β,γ-imido)triphosphate. Comparison among the two structures and other state 1 and state 2 structures of H-Ras/M-Ras reveal two new structural features playing critical roles in state dynamics; interaction of residues 31/41 (H-Ras/M-Ras) with residues 29/39 and 30/40, which induces a conformational change of switch I favoring its interaction with the γ-phosphate, and the hydrogen-bonding interaction of switch II with its neighboring α-helix, α3-helix, which induces a conformational change of switch II favoring its interaction with the γ-phosphate. The importance of the latter interaction is proved by mutational analyses of the residues involved in hydrogen bonding. These results define the two novel functional regions playing critical roles during state transition.

Prevalence and independent factors for gastroduodenal ulcers/erosions in asymptomatic patients taking low-dose aspirin and gastroprotective agents: the OITA-GF study

BACKGROUND

Although it is well known that aspirin causes gastroduodenal mucosal injury and that aspirin-induced gastroduodenal mucosal injury is often asymptomatic, the prevalence and independent factors for gastroduodenal mucosal injury have not been clarified in asymptomatic patients taking low-dose aspirin and gastroprotective agents.

AIM

To clarify the prevalence and independent factors for gastroduodenal ulcers/erosions in asymptomatic patients taking low-dose aspirin and gastroprotective agents.

DESIGN

Prospective observational study.

METHODS

We performed endoscopy in 150 asymptomatic patients taking low-dose aspirin and gastroprotective agents for at least 3 months.

RESULTS

Gastroduodenal ulcers/erosions were observed in 37.3% [ulcers (4.0%); erosions (34.0%)]. Univariate logistic regression analyses showed that proton-pump inhibitor (PPI) use was negatively associated with gastroduodenal ulcers/erosions [odds ratio (OR) 0.35, 95% confidence interval (95% CI) 0.17-0.75, P=0.007]. A multivariate logistic regression analysis selected PPI use as the only independent factor for gastroduodenal ulcers/erosions (OR 0.35, 95% CI 0.14-0.86, P=0.02). None of the 53 patients with PPI use had any gastroduodenal ulcers, and 11 with standard-dose PPI use tended to have a lower prevalence of gastroduodenal erosions than 42 with low-dose PPI use (0% vs. 28.6%, P=0.052).

CONCLUSION

Gastroduodenal ulcers/erosions were observed in about one-third of asymptomatic patients taking low-dose aspirin and gastroprotective agents, and PPI use was a negative independent factor for gastroduodenal ulcers/erosions in those patients. In addition, standard-dose PPI therapy might be more effective in the prevention of aspirin-induced gastroduodenal mucosal injury than low-dose PPI therapy.

[Combined aortic root replacement and pectus excavatum correction in Marfan's syndrome]

A 53-year-old man with Marfan's syndrome was admitted for repair of annulo-aortic ectasia (58 mm). He had also severe pectus excavatum. The skin was incised along the sternal midline. The pectoral muscles were detached laterally. After the perichondrium and costal cartilages were resected bilaterally. the left-sided intercostal muscles and perichondrial sheaths were divided 3 cm lateral to the sternum. To place the retractor in parasternal position, excellent exposure of the heart and aortic root was enabled. The aortic root was replaced with a Carboseal graft. Chest wall reconstructions was completed by modified Ravitch procedure with Gore-tex sheet The patient was discharged after an uneventful recovery on postoperative day 14.

Gadolinium enhancement of cauda equina after combined spinal-epidural anaesthesia

The occurrence of neurological symptoms after spinal anaesthesia has been reported with several local anaesthetics including lidocaine, prilocaine, mepivacaine, tetracaine and bupivacaine. Although hyperbaric bupivacaine is known to induce neurological symptoms less frequently than lidocaine, a few cases of cauda equina syndrome (CES) following the intraspinal injection of bupivacaine have been reported in the English literature. We describe lumbar MRI findings for a 29-year-old woman presenting with CES after caesarean section.

Structural basis for conformational dynamics of GTP-bound Ras protein

Ras family small GTPases assume two interconverting conformations, "inactive" state 1 and "active" state 2, in their GTP-bound forms. Here, to clarify the mechanism of state transition, we have carried out x-ray crystal structure analyses of a series of mutant H-Ras and M-Ras in complex with guanosine 5'-(beta,gamma-imido)triphosphate (GppNHp), representing various intermediate states of the transition. Crystallization of H-RasT35S-GppNHp enables us to solve the first complete tertiary structure of H-Ras state 1 possessing two surface pockets unseen in the state 2 or H-Ras-GDP structure. Moreover, determination of the two distinct crystal structures of H-RasT35S-GppNHp, showing prominent polysterism in the switch I and switch II regions, reveals a pivotal role of the guanine nucleotide-mediated interaction between the two switch regions and its rearrangement by a nucleotide positional change in the state 2 to state 1 transition. Furthermore, the (31)P NMR spectra and crystal structures of the GppNHp-bound forms of M-Ras mutants, carrying various H-Ras-type amino acid substitutions, also reveal the existence of a surface pocket in state 1 and support a similar mechanism based on the nucleotide-mediated interaction and its rearrangement in the state 1 to state 2 transition. Intriguingly, the conformational changes accompanying the state transition mimic those that occurred upon GDP/GTP exchange, indicating a common mechanistic basis inherent in the high flexibility of the switch regions. Collectively, these results clarify the structural features distinguishing the two states and provide new insights into the molecular basis for the state transition of Ras protein.

Terahertz time-domain spectroscopy of poly-L-lysine

Poly-L-lysine is known to have three different secondary structures depending on solvent conditions because of its flexible nature. In previous work (Kambara et al., Phys Chem Chem Phys 2008, 10, 5042-5044), we observed two different types of structural changes in poly-L-lysine. In the present study, we investigated the low-frequency spectrum of poly-L-lysine with a beta-sheet structure in the solid state by terahertz time-domain spectroscopy. On the basis of this spectroscopic analysis, we found that the low-frequency dynamics differed from those of other polypeptides. Furthermore, we performed powder X-ray diffraction measurement on poly-L-lysine, which was found to be highly amorphous compared with other polypeptides.

Designed low amphipathic peptides with alpha-helical propensity exhibiting antimicrobial activity via a lipid domain formation mechanism

Although several low amphipathic peptides have been known to exhibit antimicrobial activity, their mode of action has not been completely elucidated. In this study, using designed low amphipathic peptides that retain different alpha-helical content and hydrophobicity, we attempted to investigate the mechanism of these properties. Calorimetric and thermodynamic analyses demonstrated that the peptides induce formation of two lipid domains in an anionic liposome at a high peptide-to-lipid ratio. On the other hand, even at a low peptide-to-lipid ratio, they caused minimal membrane damage, such as flip-flop of membrane lipids or leakage of calcein molecules from liposomes, and never translocated across membranes. Interaction energies between the peptides and anionic liposomes showed good correlation with antimicrobial activity for both Escherichia coli and Bacillus subtilis. We thus propose that the domain formation mechanism in which antimicrobial peptides exhibit activity solely by forming lipid domains without membrane damage is a major determinant of the antimicrobial activity of low amphipathic peptides. These peptides appear to stiffen the membrane such that it is deprived of the fluidity necessary for biological functions. We also showed that to construct the lipid domains, peptides need not form stable and cooperative structures. Rather, it is essential for peptides to only interact tightly with the membrane interface via strong electrostatic interactions, and slight differences in binding strength are invoked by differences in hydrophobicity. The peptides thus designed might pave the way for "clean" antimicrobial reagents that never cause release of membrane elements and efflux of their inner components.

Case report. Primary hypothalamic third ventriclular Burkitt's lymphoma: a case report with emphasis on differential diagnosis

A patient with primary Burkitt-type lymphoma of the central nervous system is presented. A hypothalamic-third ventricular tumour in a man 71 years of age was diagnosed histologically as Burkitt's lymphoma. Primary Burkitt's lymphoma of the hypothalamic region is extremely rare and has not been previously reported in adults.

Therapy for nifedipine-induced gingival overgrowth by Saireito in rats

Objective

A calcium antagonist, nifedipine, causes gingival overgrowth as a side effect. It has been confirmed that the Japanese traditional medicine, Saireito, inhibits the nifedipine-induced proliferation of gingival fibroblasts in vitro. We performed an in vivo experiment to determine whether Saireito has a therapeutic use in the treatment of nifedipine-induced gingival overgrowth.

Methods

The rats had significant gingival overgrowth induced by the administration of nifedipine. The space between the submandibular incisors and the width of buccal gingiva of maxillary left first molar were macroscopically measured. The buccal gingiva was microscopically examined.

Results

Eight weeks after Saireito was administrated together with nifedipine, Saireito decreased both the incisor space and the gingiva width which had been enlarged by nifedipine and furthermore, the area of connective tissue of nifedipine + Saireito group was significantly smaller than that of nifedipine alone.

Conclusion

In conclusion, Saireito may be clinically effective in therapy for calcium antagonist-induced gingival overgrowth.

Lupus cystitis: a case report and review of the literature

Lupus cystitis is a rare complication associated with systemic lupus erythematosus (SLE). This rare disorder has been reported mainly from East Asia, especially from Japan. In this study, we describe a patient with lupus cystitis and review 37 reported cases in Japan. Bowel symptoms preceded urinary symptoms in 13 of 37 (35%) patients, whereas five patients complained of only bowel symptoms. Hydronephrosis was detected in 34 of 37 patients (92%). The possibility of lupus cystitis should be considered when patients complain of bowel or urinary symptoms. Examination for hydronephrosis is critical for diagnosis.

The effects of antibiotics on in vitro biofilm model of periodontal disease

OBJECTIVE

Periodontal disease is considered to be a bio?film infectious disease. The effects of macrolide and tetracycline on biofilm were examined in in vitro biofilm model made of periodontal disease-associated bacteria.

METHODS

Biofilms were made on salivary pellicle by adding Streptococcus gordonii for 2 days, followed by Porphyromonas gingivalis inoculation for 2, 5, or 12 days. Biofilms were treated with macrolide antibiotics; erythromycin (EM), azithromycin (AZM) and josamycin (JOM) and tetracycline antibiotic, minocycline (MINO). The effects of these antibiotics on biofilms were examined using colorimetric quantification method, scanning electron microscope (SEM) and confocal laser scanning microscopy (CLSM).

RESULTS

When antibiotics were added to the biofilm 2 days after inoculation of Porphyromonas gingivalis (biofilm inhibition model), all four antibiotics decreased the number of bacteria by both colorimetric method and SEM observation. When antibiotics were added to biofilms 5 or 12 days after inoculation (biofilm destruction model), those in biofilms were decreased by EM and AZM compared with JOM and MINO. Moreover, CLSM observation demonstrated that EM and AZM killed bacteria in biofilm more deeply than JOM and MINO.

CONCLUSION

These results suggest the feasibility of EM and AZM for the treatment of periodontal disease as a biofilm infectious disease.

Application of devices for safe laparoscopic hepatectomy

The continuing evolution of a variety of laparoscopic instrument and device has been gradually applied to the laparoscopic hepatectomy in many countries. Recent experience has persuaded us that there are great potential benefits derived from laparoscopic hepatectomy and much has been learned about patient selection, the grade of surgical difficulty with respect to tumor location, and the required instrumentation. Among these efforts, various ways of hepatic parenchymal transection with mechanical devices have been attempted and continuing to innovate to perform safe laparoscopic hepatectomy Important technologic developments and improved endoscopic procedures are being established equipment modifications. For safe laparoscopic hepatectomy, it is important to have all necessary equipment. The intraoperative laparoscopic ultrasonography, microwave coagulators, ultrasonic dissection, argon beam coagulators, laparoscopic coagulation shears, endolinear staplers and TissueLink monopolar sealer are essential. This procedure is in need that well experienced endoscopic surgeon and well-experienced liver surgeon should be collaborated in laparoscopic hepatectomy and the indications are strictly followed based upon the location and size of tumors. Finally critical determinant for success and safe laparoscopic hepatectomy is through familiarity with the relevant laparoscopic instruments and equipments. Laparoscopic hepatectomy is expected to develop further in the future as a new surgical instrument, equipment and method, which improves patients' quality of life.

Detection of human papillomavirus type 56 in Bowen's disease involving the nail matrix

BACKGROUND

As Bowen's disease of the nail apparatus is quite rare, there have been only a few reports on the prevalence of human papillomavirus (HPV) infection in this condition.

OBJECTIVES

The purpose of this study was to clarify the association of HPV with this disease involving the nail apparatus.

METHODS

Five patients with Bowen's disease of the nail apparatus were investigated clinically, virologically and histologically. Total DNAs extracted from excised skin lesions were analysed using polymerase chain reaction (PCR) for the presence of HPV DNA and the amplified products were subjected to DNA sequence analyses. Histological localization of HPV DNA was examined by in situ hybridization.

RESULTS

In three of five patients, HPV was detected by PCR amplification, and subsequent sequence analyses of the PCR products showed the sequences of HPV type 56. A common clinical feature of the three HPV-positive patients was longitudinal melanonychia. In contrast, the two HPV-negative patients presented with a convex nail deformity and a periungual ulcerative lesion. In two of three positive cases, there was a silent point mutation in the L1 gene of each HPV. In the remaining one case, the nucleotide sequence was consistent with the consensus sequence of HPV 56. Sequence analyses of the E6 gene revealed the infection of different variants of HPV 56 among the three cases. The viral genomes were located in keratinocyte nuclei upon in situ hybridization.

CONCLUSIONS

HPV 56 may be involved in the carcinogenesis of Bowen's disease affecting the nail matrix with longitudinal pigmentation.

Steplike lattice deformation of single crystalline (La0.4Pr0.6)1.2Sr1.8Mn2O7 bilayered manganite

We report a steplike lattice transformation of single crystalline (La0.4Pr0.6)1.2Sr1.8Mn2O7 bilayered manganite accompanied by both magnetization and magnetoresistive jumps, and examine the ultrasharp nature of the field-induced first-order transition from a paramagnetic insulator to a ferromagnetic metal phase accompanied by a huge decrease in resistance. Our findings support that the abrupt magnetostriction is closely related to an orbital frustration existing in the inhomogeneous paramagnetic insulating phase rather than a martensitic scenario between competing two phases.

The significant influence of smoking status and gender on the clinical outcome in the patients with non-small cell lung cancer: The large cohort based study

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Background: To determine retrospectively whether smoking status and gender affect the treatment outcome and survival for the Japanese patients with non-small cell lung cancer. Methods: Using the database from the lung cancer registry of the National Hospital Study Group for Lung Cancer between 1987 and 2002, detailed demographic and survival information were obtained. A total of 18,346 (70%) documented smokers including the former and the current and 7,755 (30%) documented never smokers with non-small cell lung cancer were studied. A minimal follow-up period was two years. Among them, the 2,546 patients with stage IV lung adenocarcinoma were studied to examine the relationship between the smoking status or the gender and the chemotherapy effect. Multivariate analysis was performed using the Cox regression method. Results: There was an increased percentage of female subjects (72%) in the never smokers, and an increased percentage of male subjects (90%) in the smokers. The never smokers had lower performance status (PS) and lower clinical stage than the smokers (p<0.001). There was an increased percentage of adenocarcinoma (83%) in the never smokers. Multivariate analysis for all the patients demonstrated that the lower clinical stage, the lower PS, younger age, female and never smoking was an independent good prognostic factor The hazard ratio (HR) and its 95% CI was 3.73 (3.58–3.88), 2.69 (2.59–2.79), 1.21 (1.17–1.25), 1.15 (1.09–1.20), and 1.08 (1.04–1.14), respectively. Multivariate analysis for the stage IV adenocarcinoma also showed that the lower PS, female and never smoking was an independent good prognostic factor. The HR and its 95% CI was 2.37 (2.15–2.61), 1.35 (1.19–1.52) and 1.17 (1.04–1.32) respectively. In the treatment of chemotherapy for the stage IV adenocarcinoma patients, the never smokers had higher disease control rates (CR+PR+SD) than the smokers (p=0.08) and the females had higher response rates (CR+PR) than the males (p=0.02). Conclusions: The never smokers and females with non-small cell lung cancer were found to have a distinct and improved clinical outcome.

No significant financial relationships to disclose.