Regular conductance fluctuations indicative of quasi-ballistic transport in bilayer graphene.

Quasi-periodic conductance fluctuations are observed in the low-temperature magneto-conductance of a bilayer graphene sample. The quasi-periodic nature of the fluctuations is confirmed by their Fourier power spectrum, which consists of just a small number of dominant frequency components. From an experimental study of these features, which are highly reminiscent of those reported previously for ballistic semiconductor quantum dots, we suggest that they are associated with the formation of an open quantum dot in the submicron graphene sample.

An improvement of the Ames test using a modified human liver S9 preparation.

INTRODUCTION: In preliminary studies on the Ames test using human liver S9 fractions, we found that the crude human S9 fractions, obtained following centrifugation of the tissue homogenate for 20 min at 9000 x g, were not always sterile. When this was the case, the S9 fractions were often accompanied by an increased number of colonies above the normal range on plates in the solvent control used in the Ames test. In addition, we also sometimes identified the incorporation of a small amount of fat in the crude human liver S9 fractions. We have therefore obtained a purified fat-free S9 fraction by a simple modification to the crude S9 preparation; fat was completely removed by centrifugation of the crude S9 fraction. METHODS: Using the purified and crude human S9 fractions (two lots each), both the sterility and the number of bacterial colonies produced on a plate with five bacterial tester strains by solvent controls (purified water and dimethyl sulfoxide) were examined. The findings were then compared to those observed with phosphate buffer or S9 fraction from rats pretreated with phenobarbital/5,6-benzoflavone. RESULTS: The data show that each of the crude human S9 fractions was not sterile and produced an increasing number of colonies with each solvent control, almost equal to the sum of the numbers of contaminating bacterial colonies and spontaneous revertant colonies observed with phosphate buffer or the rat S9 fraction. On the other hand, both the purified human S9 fractions were sterile, and the number of colonies that appeared in each solvent control was similar to that of spontaneous revertant colonies observed with phosphate buffer or the rat S9 fraction. DISCUSSION: These results indicate that this new procedure of S9 preparation, modified with an additional recentrifugation step, may provide a high quality of purified fat- and bacteria-free S9 fraction for use in the Ames test.

Well maintained expression of CYP genes in sandwich-culturing hepatocytes: quantitative analysis using real-time PCR method.

Sandwich-culturing is an excellent hepatocyte culturing method in drug metabolism studies, however, its advantages for gene expression of cytochrome P450 (CYP) have not been evaluated so far. The present study was undertaken to determine the utilities of sandwich-culturing hepatocytes for evaluation of CYP genes expression. Hepatocytes from male rats were cultured for 5 days between two layers of type-I collagen gel (sandwich-culturing) or over type-I collagen gel (single gel culturing). To determine the expression of CYP genes rapidly and accurately, the time course study using real-time RT-PCR quantification was conducted in the present study, and CYP2B1, CYP2B2, CYP3A2, CYP3A9 and CYP3A23 genes were measured. Albumin secretion was also measured by ELISA to evaluate cell viability. Higher expression and excellent maintenance of all CYP genes were confirmed in sandwich-culturing hepatocytes than those in single gel culturing. Particularly, significant difference in the amounts of CYP genes expression was observed between both methods after 3 days culturing. Albumin secretion was also higher in sandwich-culturing after 3 days culturing, suggesting that the cell viability of hepatocytes was maintained. These results indicate that sandwich-culturing method is much more advantageous than the ordinate method in maintaining the CYP gene expression and cell viability.

Pituitary carcinoma of pars distalis as a common neoplasm in Fischer-344 rats.

The incidence of invasive spontaneous pituitary carcinomas in Fischer-344 rats were studied. The pituitaries were examined histopathologically together with surrounding tissues including sphenoid bone. The incidence of carcinoma was higher than that previously reported in Fischer-344 rats. All the carcinomas observed in this study showed evidence of local invasion either ventrally into bone and bone marrow or laterally into peripheral nerves and blood vessels. No dorsal infiltration into the brain was recognized. Pituitary carcinoma with local invasion is a relatively common neoplasm when examined histopathologically together with the surrounding tissues.

[Diagnosis of colon cancer (depth of invasion) by barium enema examination; present condition].

Accuracy of the barium enema examinations in diagnosis of the depth of invasion of the small carcinomas of the colon was reviewed. The materials included 101 sessile carcinomas and 12 small advanced carcinomas that were 20 mm or less in diameter. The carcinomas with stalks and the depressed type early carcinomas (Type IIc) were excluded from the study, because the former were impossible to the nature by X-ray examinations and the latter were extremely rare. Presence of the depressed portions on the surface of the elevated lesions observed in the frontal views and the degree of the deformity observed in the profile views of the lesions were correlated with the pathological specimen and the accuracy of the radiological diagnosis of the depth of invasion was estimated. The cases with gross malignant cell invasion into the submucosal or the deeper layers were diagnosed correctly with present radiological diagnostic criteria. But, those with a small amount of malignant cell invasion into the submucosal layer or the cases with malignant cell invasion limited to the mucosal layer (intramural cancer) were not always correctly diagnosed and there was a variety in diagnosis of the depth of invasion in this group. With the current radiological techniques, proper profile views of the lesions were not obtained in quite a few cases, nor the surface characteristics of the small elevated lesions were well documented. It would probably be possible to improve these techniques and to improve diagnostic accuracy to some extent, but with certain limitations.

Angiographic difference in coronary artery of man, dog, pig, and monkey.

Comparative morphological studies on the coronary arteries of the left ventricular free wall were carried out on human, dog, pig, and monkey hearts by using postmortem coronary arteriography, soft X-ray photograms, and the clearing method. The results showed that the types of coronary arteries (types I, II, and III) and connecting portion of anastomotic vessels in the pig and monkey hearts closely resembled those in man. Whereas the dog hearts showed the following characteristics: numerous Type III vessels and anastomoses in the epicardial layer, the existence of only the left predominant type of coronary artery, and the supply of blood to the papillary muscles of the left ventricle mostly through a single branch of the coronary artery. Therefore, it is necessary to take into consideration the basic difference in the structure of the coronary arteries of human and dog hearts, when dogs are used experimentally for research of human ischemic heart disease. The fact that only the papillary muscles of the human heart-compared to animal hearts-are supplied blood from two sources may be advantageous to rescue the papillary muscles from ischemic necrosis.