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Biomedical subjects

N Chiba

Publications and source records attributed to N Chiba.

At least 127 records · Page 7Linked to original sources
PubMed1984

The DNA sequence encoding pldA gene, the structural gene for detergent-resistant phospholipase A of E. coli.

The nucleotide sequence of the pldA gene of Escherichia coli K-12, which codes for detergent-resistant phospholipase A (DR-phospholipase A), located in the outer membrane, was determined and the amino acid sequence of DR-phospholipase A was deduced. DR-phospholipase A contains 269 amino acids, resulting in a protein with a molecular weight of 30,809. It does not contain any cysteine residues and seems to be synthesized first as a precursor with a typical signal peptide composed of 20 amino acids. The NH2-terminus of the mature protein is glutamine, a polar amino acid, while other outer membrane proteins so far determined have a nonpolar amino acid there. The hydropathy profile of the deduced amino acid sequence of DR-phospholipase A was studied. Most of the region was rather hydrophilic and there were no stretches of hydrophobic amino acids. Computer analysis showed that there are no homologies between DR-phospholipase A and other extracellular phospholipases whose amino acid sequences are known. The candidates for the promoter region of the pldA gene, the 5'-flanking region, have a significantly high AT content, while the AT content of the coding region is about the same as the average AT content of the E. coli chromosome. A typical rho-independent transcription termination site is also present at the 3'-flanking region. This is the first example of the primary structure of a membrane-bound phospholipase.

Amino Acid Sequence↗
PubMed1984

Preparation of complement fixation antigen of Chlamydia psittaci grown in tissue culture by treatment with beta-propiolactone.

A new method of preparing a chlamydial complement fixation (CF) antigen by treatment with beta-propiolactone (BPL) is presented. Chlamydia psittaci strains Pigeon-1041 and Budgerigar-No. 1, and Chlamydia trachomatis strain L2/434/BU, propagated in L-929 cell monolayers, were inactivated with BPL. This BPL-treated antigen was useful for detecting CF antibodies in both human and pigeon sera, and it did not cause false-positive reactions, as are sometimes observed between some human sera and phenol-treated antigen derived from eggs. When this CF antigen was treated with potassium periodate and tested for reactivity with mouse immune ascitic fluid, it was found that the antigen contained type- or strain specificity as well as genus specificity. Immunization with the BPL-treated antigen elicited type- or strain-specific neutralizing antibody.

Animals↗
PubMedDate not supplied

Hematopoietic cells in cultures of the murine embryonic aorta-gonad-mesonephros region are induced by c-Myb.

Definitive hematopoiesis begins in the para-aortic, splanchnopleural (P-Sp) and aorta-gonad-mesonephros (AGM) regions of mouse embryos and then switches to the fetal liver [1] [2] [3]. Gene-targeted mice lacking the c-Myb transcription factor have severe hematopoietic defects in the fetal liver [4]. The role of c-Myb, if any, in P-Sp/AGM hematopoiesis has not been examined, however. Recently, we reported that oncostatin M can effectively expand both hematopoietic and endothelial-like cells from in vitro cultures of the AGM region [5]. Using this cell culture system, we examined the involvement of c-Myb in definitive hematopoiesis in the P-Sp and AGM regions. When primary cultures from the P-Sp or AGM regions of wild-type mouse embryos were probed with an anti-c-Myb antibody, hematopoietic cells but not endothelial-like cells showed positive staining. In contrast, in the P-Sp/AGM culture from c-myb(-/-) embryos, no hematopoietic cells were generated and endothelial-like cells predominated, indicating that the impairment of hematopoiesis in the liver of c-myb(-/-) embryos is actually preceded by a defect in P-Sp/AGM hematopoiesis. Hematogenic precursor cells were, however, still present in an inert but competent form among the endothelial-like, adherent cell population of c-myb(-/-) P-Sp/AGM cultures. When infected with a retrovirus carrying c-myb cDNA, these cultures gave rise to a significant number of hematopoietic cells. The rescued cells, unlike wild-type hematopoietic cells, were negative for c-Kit (a marker of hematopoietic progenitors), but did express other hematopoietic cell surface markers such as Mac-1, Gr-1 (myeloid markers), CD19, B220, Thy-1.2 (Iymphoid markers), and Ter119 (an erythroid marker). Thus, c-Myb plays a role in the generation of hematopoietic cells in the embryonic P-Sp and AGM regions.

3T3 Cells↗
PubMedDate not supplied

Dynamic etching method for fabricating a variety of tip shapes in the optical fibre probe of a scanning near-field optical microscope.

A novel etching method for an optical fibre probe of a scanning near-field optical microscope (SNOM) was developed to fabricate a variety of tip shapes through dynamic movement during etching. By moving the fibre in two-phase fluids of HF solution and organic solvent, the taper length and angle can be varied according to the movement of the position of the meniscus on the optical fibre. This method produces both long (sharp angle) and short (wide angle) tapered tips compared to tips made with stationary etching processes. A bent-type probe for a SNOM/AFM was fabricated by applying this technique and its throughput efficiency was examined. A wide-angle probe with a 50 degrees angle at the tip showed a throughput efficiency of 3.3 x 10(-4) at a resolution of 100 nm.

Journal Article↗
PubMedDate not supplied

High-speed scanning by dual feedback control in SNOM/AFM.

We have developed a high-speed scanning near-field optical microscope (SNOM)/atomic force microscope (AFM) system including dual feedback controllers. The system includes an additional piezoelectric actuator with fast response in the z direction and a correction circuit to eliminate unnecessary components from the feedback signal. From the measurement of a patterned chromium layer of 2 x 2 microm2 checks on a quartz glass plate, we confirmed that our system had more effective feedback control and faster scanning than current SNOM/AFM systems that use only a piezo-tube. The scanning speed of the present system was estimated to be about five times faster than that of current SNOM/AFM systems.

Journal Article↗
PubMedDate not supplied

Optical microcantilever consisting of channel waveguide for scanning near-field optical microscopy controlled by atomic force.

We develop a novel optical microcantilever for scanning near-field optical microscopy controlled by atomic force mode (SNOM/AFM). The optical microcantilever has the bent channel waveguide, the corner of which acts as aperture with a large tip angle. The resonance frequency of the optical microcantilever is 9 kHz, and the spring constant is estimated to be 0.59 N/m. The optical microcantilever can be operated in contact mode of SNOM/AFM and we obtain the optical resolution of about 200 nm, which is as same size as the diameter of aperture. We confirm that the throughput of optical microcantilever with an aperture of 170 nm diameter would be improved to be more than 10(-5).

Journal Article↗
PubMedDate not supplied

A Canadian physician survey of dyspepsia management.

OBJECTIVE: To determine the management of patients with new onset dyspepsia by Canadian family physicians. METHODS: A survey was mailed to 195 family physicians in August 1995 to identify how they manage dyspepsia in patients according to four scenarios: based on presenting symptoms alone; assuming Helicobacter pylori-positive; known to be H pylori-negative; and endoscopically confirmed nonulcer dyspepsia. RESULTS: A total of 170 of 195 physicians (87.2%) completed the survey. Physicians reported that 7.3% of their practice is devoted to dyspepsia and 23% of these dyspeptic patients present for the first time. Ninety-three per cent of family physicians find a symptom classification of ulcer-, reflux- and dysmotility-like dyspepsia helpful. The majority of patients are advised to make life-style changes and are treated with antacids or empiric drug therapy. A H2 receptor antagonist was the drug of choice for ulcer and reflux-like dyspepsia, while prokinetics were often used for reflux and dysmotility-like dyspepsia. After failure of initial treatment, patients were given another course of empiric treatment, commonly with cisapride or omeprazole. Family physicians estimated that the mean time to obtain a gastrointestinal consult was five weeks, and 70% indicated that this time to consult adversely influenced their decision to refer. If this time was reduced to less than two weeks, responding physicians would consider referring all eligible patients. On average, two to 2.5 courses of empiric therapy were given before referral. If H pylori status was known, fewer empiric treatments (mean 1.8) were given before gastroenterological referral compared with the other scenarios. If the patient had nonulcer dyspepsia, 30% of family physicians provided reassurance only and did not prescribe empiric drug treatment. CONCLUSIONS: Most newly dyspeptic patients in Canada are treated with empiric therapy according to symptom classification and referred for endoscopy after an average two to 2.5 treatment courses.

Adult↗