Synthesis of Silica Nanotube Using Myelin Figure as Template and their Formation Mechanism

Silica nanotubes are synthesized through a sol-gel reaction of tetraethyl orthosilicate (TEOS) using myelin figures of Pluronic P123 as the structure-directing agent. The simultaneous progression of the formation of molecular assemblies that act as templates and the formation of silica frameworks though a sol-gel reaction of the silica precursor is a characteristic of this reaction system. The synthesized silica nanotubes were characterized using transmission electron microscopy (TEM), nitrogen adsorption/desorption measurements, and Fourier-transform infrared spectroscopy (FT-IR). The silica nanotubes were unilamellar with diameters of approximately 30 nm, membrane thicknesses of approximately 10 nm, and lengths exceeding a few hundred nanometers. The Brunauer-Emmett-Teller (BET) specific surface area was 589.46 m(2)/g. Silica nanotubes can also be obtained using other Pluronic surfactants that can form myelin figures. In this work, we also investigated the formation mechanism of the silica nanotubes. The typical diameter of a myelin figure is a few tens of micrometers. However, myelin figures with diameters of approximately 10 µm can form in systems with TEOS because bifurcation is induced by minute silica nuclei that form during the initial reaction between TEOS and water. Freeze fracture TEM (FF-TEM) observations revealed the existence of myelin figures with diameters of 20 to 30 nm, which are the same size and shape as the synthesized silica nanotubes. These results indicate that bifurcation of the myelin figures is induced by the silica nuclei that form via the initial reaction of TEOS, which result in the formation of bifurcated myelin figures with diameters of ~10 µm. Myelin figures with diameters of 20 to 30 nm form on the surface, and they become templates where the reaction of TEOS progresses to form silica nanotubes with diameters of approximately 30 nm.

OmpC and OmpF are required for growth under hyperosmotic stress above pH 8 in Escherichia coli

AIMS

To investigate the requirement of outer membrane porins for osmotic adaptation at alkaline pH in Escherichia coli.

METHODS AND RESULTS

Escherichia coli mutants deficient in ompC, ompF and both genes were constructed and the growth of these mutants was observed at alkaline pH. The growth rate of the mutant deficient in both ompC and ompF was slower than that of the wild type and mutants deficient in one of these genes under hyperosmotic stress at pHs above 8.0. The decreased rate was recovered when a cloned ompC was introduced to the mutant, but the growth recovery with a cloned ompF was partial. Such growth diminution was not observed at pHs below 8.0.

CONCLUSION

OmpC and OmpF were shown to participate in hyperosmotic adaptation at alkaline pH in E. coli.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study is the first report to demonstrate that OmpC and OmpF are required for hyperosmotic adaptation at pHs above 8.0, but not below 8.0.

Carbon dioxide increases acid resistance in Escherichia coli

AIMS

To investigate how carbon dioxide affects the acid resistance of Escherichia coli.

METHODS AND RESULTS

Escherichia coli W3110 was grown in minimal EG medium at pH 7.5, and cells were adapted at pH 5.5 at 37 degrees C with and without supply of carbon dioxide and nitrogen gases. The number of colonies grown on LB medium was measured after cells were challenged in minimal EG medium of pH 2.5 at 37 degrees C under various conditions. When carbon dioxide was supplied at both the acid adaptation and challenge stages, 94% of cells survived after the acid challenge for 1 h, while the survival rates were 50 and 67% when nitrogen gas and glutamate were supplied respectively. After the acid challenge for 3 h, the survival rate observed with the carbon dioxide gas supply was again 2.5-fold higher than those with the nitrogen gas supply.

CONCLUSION

Carbon dioxide was shown to participate in the maintenance of high viability under acidic conditions.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study provides useful information for research into bacterial pathogenesis, fermentation and food preservation.

Quantitative analysis of endothelin-1 and vasoactive intestinal contractor/endothelin-2 gene expression in rats by real-time reverse transcriptase polymerase chain reaction

We established a real-time quantitative reverse transcriptase polymerase chain reaction (RT-PCR) system for the analysis of rat endothelin-1 (ET-1) and vasoactive intestinal contractor (VIC)/ET-2 gene expression. We used this technique to examine the expression levels in rat in 16 different organs. ET-1 gene expression was observed in all organs examined, while VIC mRNA was detected in some organs such as heart, lung, ovary, stomach, and intestine. Ovary and intestine express both ET-1 and VIC mRNA at high levels, suggesting the importance of both peptides in these organs. In addition, we examined the gene expression levels in intestinal epithelial and mesenchymal tissues from rat fetuses at 16.5 and 19.5 days postcoitus (E16.5 and E19.5). We observed distinct differences in the temporal gene expression patterns for ET-1 and VIC in fetal intestinal epithelial tissue. In fetal mesenchymal tissue the expression level of ET-1 is significantly higher than that of VIC, and the levels of both genes remain unchanged over the time period observed. These findings suggest distinct biological roles and gene regulation mechanisms for ET-1 and VIC in intestinal epithelial and mesenchymal tissues.

EUS changes predictive for recurrence of esophageal varices in patients treated by combined endoscopic ligation and sclerotherapy

BACKGROUND

Recurrence of varices is still common after endoscopic treatment of esophageal varices. In this study, predictive signs of variceal recurrence were investigated by ultrasonic (US) miniature probe in patients treated by combined endoscopic ligation and sclerotherapy.

METHODS

Detectability of vessels by US miniature probe was evaluated first in rats. In 41 patients treated by combined therapy, the esophagus and the cardia region were examined by US miniature probe. In 25 patients examined by percutaneous transhepatic portography, the relationship between US miniature probe and percutaneous transhepatic portography findings was evaluated.

RESULTS

The smallest vessel detected by US miniature probe was 0.3 mm in diameter in the study using intra-abdominal vessels of rat. After variceal eradication, US miniature probe showed intramural vessels in the cardia that were classified as follows: grade I, a few vessels (19 patients, 46%); grade II, uniformly scattered vessels (11, 27%); grade III, abundant vessels resembling a honeycomb (11, 27%). As the sonographic grade increased, the rate of variceal recurrence increased. As the venographic grade of staining in the distal esophagus increased, the esophageal wall became thicker and the sonographic grade at the cardia increased.

CONCLUSIONS

Endosonographic evaluation of the distal esophagus and cardia is predictive of variceal recurrence.

An N-pattern display for an SSD X-ray diffractometer

The present paper describes a new type of display for X-ray diffraction patterns which corresponds to the N pattern well known in electron diffraction. This has been realized by an ω-circle SSD (solid-state detector) diffractometer equipped with a CRT display all operated by a small computer. The merits are described of its possible applications.