Observation of the intrinsic pinning of a magnetic domain wall in a ferromagnetic nanowire.

The spin transfer torque is essential for electrical magnetization switching. When a magnetic domain wall is driven by an electric current through an adiabatic spin torque, the theory predicts a threshold current even for a perfect wire without any extrinsic pinning. The experimental confirmation of this 'intrinsic pinning', however, has long been missing. Here, we give evidence that this intrinsic pinning determines the threshold, and thus that the adiabatic spin torque dominates the domain wall motion in a perpendicularly magnetized Co/Ni nanowire. The intrinsic nature manifests itself both in the field-independent threshold current and in the presence of its minimum on tuning the wire width. The demonstrated domain wall motion purely due to the adiabatic spin torque will serve to achieve robust operation and low energy consumption in spintronic devices.

Long-term studies on carcinogenicity and promoting effect of phenylbutazone in DONRYU rats.

The carcinogenicity and promoting effect of phenylbutazone were investigated in inbred DONRYU rats. In the carcinogenicity study, both sexes were administered the chemical at dietary levels of 0 (control), 0.125, or 0.25% for 2 years. Toxic lesions were associated with phenylbutazone treatment in the kidney and digestive tract, appearing to have an adverse effect on life expectancy. Various tumors were detected in all groups including the controls. With the exception of pheochromocytoma in the female high-dose group, no statistically significant increase in yield of any tumors, including leukemia, was apparent in the treated groups of either sex when the data were analyzed by Fisher's exact probability and/or chi-square tests. Application of an age-adjusted statistical analysis revealed a slight positive effect regarding the occurrence of pheochromocytomas, neoplastic liver nodules, and leukemias in females. However, these tumors are commonly observed to develop spontaneously in this rat strain, and no such effect was apparent in the male groups. In addition, no differences in incidences of relevant preneoplastic lesions were evident between control and treated groups. Thus phenylbutazone showed no carcinogenic activity in DONRYU rats when given continuously in the diet for 2 years. For the investigation of promoting effect, phenylbutazone was given as a dietary supplement for 2 years subsequent to initiation with N-ethyl-N-nitrosourea or N-propyl-N-nitrosourea. No enhancement of nitrosourea-induced leukemogenesis was apparent, although a slight promoting effect was demonstrated for renal and thyroid tumorigenesis.

Distribution, morphology, and gamma-aminobutyric acid immunoreactivity of horizontally projecting neurons in the macaque inferior temporal cortex.

In area TE of the macaque inferior temporal cortex, horizontal axons running parallel to the pial surface mediate interactions between laterally displaced sites across the cortex. We examined the spatial distribution and the types of cells that give rise to these horizontal axons, which are important factors in determining the nature of the lateral interactions in TE. Intracortical injections of retrograde tracers labeled columnar clusters of cells and cells diffusely scattered within TE. The clusters were 0.35 +/- 0.11 mm (mean +/- SD) in diameter and were laterally distributed up to 6 mm from the injection site. Labeled cells were found in layers 2 to 6, with only a few labeled cells seen in layer 4. The clustering of labeled cells in layers 5 and 6 was looser than that in layers 2 and 3. Intracellular staining of the retrogradely labeled cells revealed that the majority of them were typical or modified pyramidal cells, both within and between the clusters. Only a few nonpyramidal interneurons were also stained at the fringe of the tracer injection site. Consistent with these results, only a small proportion of the retrogradely labeled cells exhibited gamma-aminobutyric acid (GABA)-like immunoreactivity, mostly found within 1 mm from the injection site. The results indicate that direct horizontal interactions in TE are predominantly mediated by pyramidal or modified pyramidal cells in layers 2, 3, 5, and 6 and are primarily excitatory in nature. The contribution of GABAergic interneurons to direct horizontal interactions is restricted to only short-distance projections.

Experimental induction of ovarian Sertoli cell tumors in rats by N-nitrosoureas.

Spontaneous ovarian tumors are very rare in ACI, Wistar, F344 and Donryu rats; the few neoplasms found are of the granulosa/theca cell type. Ovarian tumors were also rare in these strains of rats when given high doses of N-alkyl-N-nitrosoureas continuously in the drinking water for their life-span; however, relatively high incidences of Sertoli cell tumors or Sertoli cell tumors mixed with granulosa cell tumors were induced in Donryu rats after administration of either a 400 ppm N-ethyl-N-nitrosourea solution in the drinking water for 4 weeks or as a single dose of 200 mg N-propyl-N-nitrosourea per kg body weight by stomach tube. Typical Sertoli cell tumors consisted of solid areas showing tubular formation. The tubules were lined by tall, columnar cells, with abundant, faintly eosinophilic, often vacuolated cytoplasm, and basally oriented, round nuclei, resembling seminiferous tubules in the testes. In some cases, Sertoli cell tumor elements were found mixed with areas of granulosa cells. The induction of ovarian Sertoli cell tumors in Donryu rats by low doses of nitrosoureas may provide a useful model for these tumors in man.

Induction of tumors in the small intestine and mammary gland of female Donryu rats by continuous oral administration of N-carboxymethyl-N-nitrosourea.

The carcinogenicity of N-carboxymethyl-N-nitrosourea (CMNU), a naturally occurring N-nitroso compound, was tested in female Donryu rats. Four groups of female Donryu rats were given 400, 200, 100, or 0 ppm of CMNU solution continuously as drinking water. The incidence of tumors was highest and the mean survival time shortest in the 400 ppm group. A dose-effect relationship was observed in the tumor incidence and the mean survival time and the incidences of tumors in all experimental groups were significantly different from those in the control group. In the 400 ppm group, tumors were detected most frequently in the small intestine, followed by the mammary gland. In contrast, most tumors were observed in the mammary gland in the other two experimental groups, although dose-dependent induction of tumors of the small intestine was also detected in these two groups. The organ specificity of CMNU is compared with that of other N-alkyl-N-nitrosourea derivatives.

Organ-specific carcinogenicity of N-methyl-N-nitrosourea in F344 and ACI/N rats.

Male and female F344 rats were continuously administered N-methyl-N-nitrosourea (MNU) in their drinking water at concentrations of 200 or 100 ppm, and both sexes of ACI/N rats were given MNU at a concentration of 200 ppm. By the 42nd week of the experiment, high incidences of brain/spinal cord tumors were observed in both strains of rats. Histologically, many of them were astrocytomas or anaplastic astrocytomas. In addition, malignant neurinomas were also detected in the spinal nerve roots and trigeminal nerves, although their incidences were rather low. There was no difference in the type and incidence of these neurogenic tumors between the two strains of rats. Tumors of the tongue and esophagus were mainly observed in the high-dose group of F344 rats and those of the glandular stomach were observed in the low-dose group of F344 rats. In ACI/N rats, tumors of the heart and renal pelvis were detected. The organ-specific carcinogenicity of MNU in these two strains of rats was compared with that of MNU in Donryu rats. It was demonstrated that organ specificity of MNU given orally was influenced not only by the strain of rats but also by the dose level.

Induction of Sertoli cell tumors in the rat ovary by N-alkyl-N-nitrosoureas.

Relatively high incidences of Sertoli cell tumors of the ovary were induced in Donryu rats given a 400 ppm N-ethyl-N-nitrosourea solution as drinking water for 4 weeks or a single dose of 200 mg/kg N-propyl-N-nitrosourea by stomach tube. Typical Sertoli cell tumors were composed of solid areas showing tubular formation. Tubules were lined by tall, columnar cells having abundant, faintly eosinophilic, often vacuolated cytoplasm, and basally oriented round nuclei. In some cases, Sertoli cell tumors were found to be mixed with granulosa cell tumors.

Malignant fibrous histiocytomas induced in rats by polymers.

Five polymeric materials (3 polyvinyl chlorides, 1 polyhydroxyethyl methacrylate, and 1 dimethyl polysiloxane) were implanted into subcutaneous (SC) tissues of rats. Subcutaneous tumors developed in all experimental groups. The incidences of the tumors differed however, although the experimental conditions were the same for all these materials. This result indicates that chemical characteristics of the materials may influence the incidence of SC tumors. From the histological and electron-microscopic findings many of these tumors were diagnosed as malignant fibrous histiocytomas.

Possible association of active gastritis, featuring accelerated cell turnover and p53 overexpression, with cancer development at anastomoses after gastrojejunostomy. Comparison with gastroduodenostomy.

To cast light on tumorigenesis in the remnant stomach after distal gastrectomy for peptic ulcer or gastric cancer, 45 cases in gastroduodenostomy (Billroth I, 17 cases) and gastrojejunostomy (Billroth II, 28 cases) groups were compared for a series of parameters. Cancers in Billroth II were significantly more predominant in the anastomosis area and more frequently associated with Epstein-Barr virus infection. Active gastritis, accelerated epithelial cell turnover (as assessed by measurements of apoptosis and cell proliferation), DNA damage, and foveolar cell hyperplasia were all greater in anastomotic areas after Billroth II than in proximal areas after Billroth II or either area after Billroth I. K-ras mutations were rare, but Epstein-Barr virus infection in cancers was seen frequently in anastomosis cases. In conclusion, active gastritis, possibly induced by enterogastric reflux, is linked to tumorigenesis in anastomosis sites in Billroth II cases.

Patterning neuronal and glia cells on light-assisted functionalised photoresists.

A common photosensitive polymeric material used in semiconductor microlithography (diazo-naphto-quinone/novolak resist) was pattern-exposed with near-UV light to create carboxylic-rich areas on the polymer surface. The patterned surfaces were further functionalised via: (1) the anchorage of peptides for specific cell-attachment or cell-detachment functions; or (2) the diffusion of silicon rich chemical species to achieve the cell detachment. Pairs of antagonistic surface characteristics controlled the cell attachment: (1) amino-rich or carboxylic-rich surfaces; and (2) hydrophilic or hydrophobic surfaces; in which the former promoted the adhesion. It was found that common microlithographic materials and techniques can be upgraded to allow an effective control of the lateral organisation of the artificial arrays of neuronal and glia cells.

Carcinogenicity study of ammonia-process caramel in F344 rats.

The carcinogenicity of ammonia-process caramel, a food colouring, was examined in F344 rats. Caramel was dissolved in distilled water at levels of 0, 1 and 4% and groups of 50 male and 50 female rats were given 20-25 ml of one of these solutions/rat/day as their drinking water for 2 yr. There were no significant differences between the total incidences of tumours or mean survival times of control and experimental groups. A variety of tumours developed in all groups including the control group, and no dose-related effects were found either in the incidence or induction time of tumours in the various organs and tissues except in the pituitary gland of males, in which the incidence of tumours in males given 4% caramel solution was significantly higher than that in controls. Pituitary tumours are among the most common spontaneous tumours in ageing rats of this strain and have a variable incidence. In addition, almost all pituitary tumours detected in males given the 4% solution were microscopic tumours, and there was no significant difference between controls and treated groups in the incidence of hyperplasia or pre-neoplastic lesions in the pituitary gland. These results indicate that the significantly higher incidence of pituitary tumours in males given the 4% caramel solution was not related to caramel administration, but could be explained by the variability of the incidence of spontaneous pituitary tumours. Thus it is concluded that under these experimental conditions ammonia-process caramel was not carcinogenic in F344 rats.

Lack of evidence of carcinogenicity of technical-grade piperonyl butoxide in F344 rats: selective induction of ileocaecal ulcers.

The carcinogenicity of technical-grade piperonyl butoxide was studied in F344/DuCrj rats fed a dietary level of 0.5 or 1% for 2 yr. Various tumours were detected in all groups, including the untreated control group, but no significant dose-related increase in the incidence of any tumour was found. Thus, it is concluded that under these experimental conditions piperonyl butoxide was not carcinogenic in F344 rats. Unexpectedly, however, ileocaecal ulcers were found in animals of both sexes in both experimental groups and the incidence was dose related. Further studies are required to establish the mechanism of induction of ileocaecal ulcers by piperonyl butoxide.

Lack of carcinogenicity of tartrazine (FD & C Yellow No. 5) in the F344 rat.

The carcinogenicity of tartrazine (C. I. Food Yellow No. 4, FD & C Yellow No. 5), a food, drug and cosmetics colouring, was examined in F344 rats. Tartrazine was dissolved in distilled water at levels of 0, 1 or 2%, and groups of about 50 male and 50 female rats were given one of these solutions ad lib. as their drinking-water for up to 2 yr. No toxic lesions specifically caused by tartrazine were detected in any treated group of either sex. Many tumours developed in all groups including the control group, and the organ distribution of these tumours and their histological characteristics were similar to those of the spontaneous tumours that are known to occur in this strain of rats. Except for mesothelioma in males and endometrial stromal polyp in females, there were no significant increases in the incidences of any tumours over those in the corresponding control group. In males, mesotheliomas were found only in the group given 1% tartrazine and the incidence of this lesion was statistically significant (Fisher's exact test) in comparison with the other two groups (P less than 0.02). The incidence of endometrial stromal polyp was also significantly higher among females given the 1% dose than in the controls (P less than 0.05). However, no positive trend was noted in the occurrence of these two tumours using an age-adjusted statistical analysis. Mesothelioma and endometrial stromal polyp are frequently observed spontaneous tumours in this strain of rats, and their incidences in our historical controls are 4.1 and 21.9%, respectively. However in the present study mesothelioma occurred in none of the male control rats and the incidence of endometrial stromal polyp was only 10.6% in the female control group. Moreover, there was no significant difference between the control and treated groups in hyperplastic or pre-neoplastic changes in the mesothelium or endometrium. From these findings, we concluded that the significant increases in the incidences of mesothelioma and endometrial stromal polyp that occurred in the groups given 1% tartrazine were not attributable to tartrazine administration. Thus, it is concluded that tartrazine was not carcinogenic in F344 rats when administered continuously at doses of up to 2% in the drinking-water for up to 2 yr.

T-cell lymphoma presenting with pericardial and pleural effusion as the initial and primary lesion: cytogenetic and molecular evidence.

A 90-year-old woman was admitted with progressive dyspnea. Chest roentgenogram and computed tomography revealed a massive pericardial effusion and bilateral pleural effusion, but no lymphomatous lesion was seen. A diagnosis of malignant lymphoma was made by cytological and immunological studies of the cells obtained from the pericardial effusion. Chromosome analysis showed a clonal abnormality and T-lineage clonality was determined by the rearrangement of the T-cell receptor gamma gene. The patient achieved remission with chemotherapy, but she later relapsed, with right pleural effusion, and died. She exhibited no lymphomatous features throughout the clinical course, indicating the possibility of malignant lymphoma originating from the pericardium and/or pleura.

Teratoma of the pituitary gland in a young male rat.

A pituitary teratoma was found in a 5-week-old (37-day-old) male Donryu rat. The tumour (10 x 11 x 9 mm) was round in shape and white in colour. The cut surface was solid without haemorrhagic or cystic change. Histologically, it was composed of various kinds of tissue components including mature and immature elements derived from the three embryonic germ layers, i.e., nervous tissue, cartilage, bone, squamous epithelial element, glandular element lined by one or more layers of ciliated columnar or cuboidal epithelial cells, striated muscle tissue, adipose tissue and connective tissue. Neuroepithelial rosettes and immature or embryonal epithelium as well as immature cartilage were intermingled with mature somatic tissues.

Effects of barbital on neuro-oncogenesis in a transplacental carcinogenicity model using F344 rats.

Effects of barbital (BB) on neuro-oncogenesis were examined in a rat transplacental carcinogenesis model. Pregnant F344 rats were divided into 7 groups. Dams in group I received subcutaneous injections of 10 mg/rat 1-butyl-1-nitrosourea (BNU) on the days 15, 18 and 21 of pregnancy and dams in groups II-IV, 1mg/rat BNU on the same time schedule. In addition to the treatment with BNU, dams in group IV were given 0.125% BB solution as their drinking water from the day 12 of pregnancy to parturition. Offspring in groups III and IV received 0.125% BB solution as drinking water from 4 weeks of age until the termination of the study. Animals in groups V and VI were given 0.25% and 0.125% BB solutions, respectively, in the peri- and postnatal period without BNU treatment. Dams in group VII received 250 mg/kg BB subcutaneously on the days 15, 18 and 21 of pregnancy. Offspring in all groups were observed until 105-116 weeks of age. High yields of neurogenic tumors, such as gliomas and neurinomas, were observed in group I. In groups II, III and IV, single cases of a chordoma, a granular cell tumor, and a neurinoma and a malignant reticulosis, which are known to occur spontaneously, were noted, although no gliomas were found. No neurogenic tumors were observed in groups V-VII. With regard to lesions other than those in neurogenic organs, a significant increase in liver tumors was observed in group III compared to group II. In contrast, lung tumors were not found in group III, while they were observed in groups II and IV. These results suggest that BB has no neuro-carcinogenic activity in the rat transplacental carcinogenesis model.

[Teratological study of 4-ethoxy-2-methyl 5-morpholino-3(2H)-pyridazinone (M73101) in mice and rats (author's transl)].

M73101 was given orally to pregnant mice (0, 100, 400 and 800 mg/kg/day) and rats (0, 100, 300 and 600mg/kg/day) during the major organogenesis to assess the influences of prenatal and postnatal development of progeny. There were no apparent effects of M73101 on litter size, fetal mortality or sex ratio in both species, although slight decrease in body weight occurred in fetuses of mice and rats exposed to the largest dose. No external, internal or skeletal malformations attributable to M73101 were observed in mouse and rat fetuses. No apparent influences of M73101 on postnatal development of mouse or rat offspring were seen.

[Reproduction study of 4-ethoxy-2-methyl-5-morpholino-3(2H)-pyridazinone (M73101) in rats (II). Administration of M73101 during the period of major organogenesis (author's transl)].

Pregnant female rats were given orally M73101 (0,100,250 and 600 mg/kg) or aspirin (225 mg/kg) on gestational days 7 to 17. About two-thirds of treated females in each group were sacrificed at day 21 of pregnancy and their fetuses were examined for abnormalities. The remaining females were allowed to deliver spontaneously in order to observe postnatal development of their offspring. The results were summarized as follows: 1. No significant effects of M73101 on number of the corpora lutea, litter size, fetal mortality, fetal weight or sex ratio were observed, but aspirin exhibited the intrauterine deaths and growth retardation in fetuses. 2. No external, internal or skeletal malformations attributable to M73101 were seen in fetuses, although aspirin caused malformations of various organ systems. 3. No apparent effects of M73101 on F1 generation were observed on postnatal development including emotionality, learning ability and reproductive performance. There were no adverse influences of M73101 on postnatal development of F2 generation. Aspirin, however, showed adverse effects on postnatal survival, growth, emotionality and mating performance of F1 generation.

[Reproduction study of 4-ethoxy-2-methyl-5-morpholino-3(2H)-pyridazinone (M73101) in rabbits. Administration of M73101 during the period of major organogenesis (author's transl)].

M73101 and aspirin were evaluated for the effects on prenatal development of progeny in JW-NIBS strain rabbits. Pregnant females were given orally M73101 (0, 50, 120 and 300mg/kg/day) or aspirin (200mg/kg/day) on days 6 to 18 of gestation. They were sacrificed on days 29 of pregnancy and their fetuses were examined for abnormalities. The results were summarized as follows: 1. During the dosing period, females received 300mg/kg of M73101 showed pronounced body weight depression and decrease in food and water intake. But after the dosing period, these influences were not seen. Females received aspirin did not show such phenomena. 2. There were no adverse effects on number of implants, litter size, fetal mortality or fetal weight, and no malformed fetuses attributable to the drugs were seen in each group.

Neoplastic and non-neoplastic lesions in aging Slc: Wistar rats.

Spontaneous neoplastic and non-neoplastic lesions in 98 male and 100 female Slc: Wistar rats, which have been widely used in Japan for toxicological studies, were examined. As spontaneous tumors, the most frequent tumors in males were testicular interstitial cell tumors, followed by tumors of the hematopoietic organs, adrenal gland, thyroid gland, preputial gland, pituitary gland, liver and mammary gland. Those in females were tumors of the pituitary gland, mammary gland, hematopoietic organs, uterus and thyroid gland. The organ distribution and histological types of spontaneous tumors observed in Slc: Wistar rats were very similar to those in F-344/DuCrj rats, although the incidences of some tumors differed slightly in the two strains. Various non-neoplastic lesions were also observed in the heart, kidney, liver and many other organs. These results should be useful in evaluating the results of toxicological and carcinogenic studies on this strain of rat.