Atom probe tomographic assessment of the distribution of germanium atoms implanted in a silicon matrix through nano-apertures.

Ion implantation through nanometer-scale apertures (nano-apertures) is a promising method to precisely position ions in silicon matrices, which is a requirement for next generation electronic and quantum computing devices. This paper reports the application of atom probe tomography (APT) to investigate the three-dimensional distribution of germanium atoms in silicon after implantation through nano-aperture of 10 nm in diameter, for evaluation of the amount and spatial distribution of implanted dopants. The experimental results obtained by APT are consistent with a simple simulation with consideration of several effects during lithography and ion implantation, such as channeling and resist flow.

Performance enhancement of semiconductor devices by control of discrete dopant distribution.

As semiconductor devices are scaled down to the nanometre level, random dopant fluctuation in the conducting channel caused by the small number of dopant atoms will significantly affect device performance. We fabricated semiconductor devices with random discrete dopant distribution in the drain side and then evaluated how well we could control the drain current of the devices. The results showed that the drain current in devices with the dopant distribution in the drain side was several per cent higher than that in devices with the dopant distribution in the source side. We believe that this increase in current is caused by the suppression of injection velocity degradation in the source side. The capability to control the location of individual dopant atoms enhances drain current and, therefore, the performance of nanodevices. Accurately controlling both the amount and the positioning of dopant atoms is critical for the advancement of true nanoelectronics.

Secondary T-cell lymphoma presenting as a giant ulcer.

Secondary cutaneous T-cell lymphoma may present with various types of skin lesions, but rarely produces ulceration in contrast to primary cutaneous T-cell lymphoma. We report a case of malignant lymphoma of the tonsil that recurred as a giant cutaneous ulcer on the back of a 45-year-old man. Biopsy of the ulcer revealed a malignant lymphoma of diffuse, mixed-cell type. Surface marker analysis of the tumour cells showed suppressor/cytotoxic T-cell characteristics. The skin lesions were treated by electron beam therapy.

Effect of retinoic acid on the infiltration of murine melanoma cells into the type I collagen gel.

Two lines of murine melanoma cells (B16 and Cloudman S91) were cultured on type I collagen gel and the effects of all-trans-retinoic acid on the growth and infiltration into the gel were assayed. In both lines, proliferation and the degree of infiltration were suppressed by the addition of all-trans-retinoic acid. The infiltration-inhibiting effect was expressed very rapidly and was dose-dependent at concentrations ranging from 10(-7) to 10(-5) M of all-trans-retinoic acid. These results suggest the anti-invasive effects of all-trans-retinoic acid on melanoma cells.

A case of prurigo pigmentosa considered to be contact allergy to chromium in an acupuncture needle.

A 53-year-old male developed prurigo pigmentosa on his back, after undergoing acupuncture for 3 years. The eruptions were ceased on discontinuing the therapy but recurred with its resumption. The acupuncture needle contained 18.12% chromium. Erythema was induced by patch testing with potassium dichromate, and a flare-up was observed in the area of the patch test on resumption of acupuncture. We consider that the eruptions were induced by contact allergy to the chromium component of the acupuncture needles.

Effects of ryo-kan-kyomi-sin-ge-nin-to extract on degranulation of and histamine release from rat mast cells.

The effects of Ryo-kan-kyomi-sin-ge-nin-to (RKSG)) extract, a medicinal agent traditionally used in China and Japan for treatment of asthma, on the degranulation of and histamine release from rat mast cells were studied. At a concentration of 5 mg/ml RKSG, degranulation of mast cells stimulated either by antigen (DNP-Ascaris) or compound 48/80 was markedly suppressed. At a concentration of 1-5 mg/ml RKSG, histamine release from mast cells due to application of either antigen or compound 48/80 was inhibited in a dose-dependent fashion. These results suggest that RKSG may be useful for the treatment of type I allergy-related diseases.

Effect of PUVA radiation on anaphylactic histamine release from rat dermal tissues.

We have devised a new in vitro model of type I cutaneous anaphylaxis. Male albino rats were sensitized with DNP-Ascaris. Abdominal skin was shaved, and thin, split-thickness slices of skin were cut with a dermatome. The dermis was excised and cut into 100 mg pieces. The dermal tissue was incubated with antigen in Tyrode's solution for 30 min at 37 degrees C. Antigen-induced histamine release from dermal tissue was measured fluorimetrically. Using this system, we measured histamine release from PUVA-irradiated and non-irradiated dermal tissues. A single PUVA irradiation inhibited type I cutaneous anaphylaxis, but did not affect spontaneous histamine release or total dermal histamine. Our model is considered to be useful for investigation of the mechanism of suppression of type I cutaneous anaphylaxis by PUVA.

Effect of tretinoin on collagen gel contraction induced by mouse 3T3 fibroblasts.

Balb/3T3 fibroblasts were cultured in type I collagen gel and the effects of tretinoin (all-trans-retinoic acid) were examined on cell growth and the gel contraction produced by cells. Cell proliferation was suppressed and the degree of gel contraction was enhanced by the addition of 10(-7) and 10(-6) M tretinoin. Growth and gel contractility of transformed cells derived from the Balb/3T3 cells were not influenced by this agent. Addition of 12-O-tetradecanoylphorbol ester, which is known to antagonize tretinoin in several biological processes, enhanced gel contraction synergistically with tretinoin. These results suggest that tretinoin influences cell-to-collagen interactions.

Infiltration of melanoma cells into the type I collagen gel.

Melanoma cells were cultured on type I collagen gel, and the infiltration of of those cells into the gel was observed. B16 murine melanoma cells initially adopted a spherical form on the gel, but they assumed a dendritic form after infiltration into the interior. The degree of infiltration increased very rapidly and was time-dependent. No correlations between the growth rate or melanogenic activity and infiltrative potential were observed. When Syrian hamster and human melanoma cell lines were cultured, the degrees of infiltration varied. This culture system using collagen gel is considered to be a useful in vitro model of tumor cell invasion.

Effects of human recombinant tumor necrosis factor-alpha (TNF-alpha) on the proliferative potential of human keratinocytes cultured in serum-free medium.

The effects of human recombinant tumor necrosis factor-alpha (TNF-alpha) on human keratinocytes cultured in a serum-free medium were investigated. TNF-alpha markedly suppressed cell growth. The growth-inhibitory effect was reversible and cytostatic at a concentration of 1-5 U/ml, but appeared to be irreversible and cytocidal at 10 U/ml. The growth suppressive effect was more marked when TNF-alpha was added in the late growth phase or preconfluent phase than when it was added in early or mid-growth phases. No effects of TNF-alpha on cell adhesion to the substrate were observed. These results indicate that TNF-alpha is a very potent anti-proliferative agent for human keratinocytes.

Proliferative potential of murine melanoma cells cultured in or on collagen gel.

As the first step in developing an in vitro model of melanoma cells infiltrating the dermis, B16 murine melanoma cells were cultured on and in type I collagen gels. Under these conditions, the melanoma cell adopted an elongated or dendritic form. Cell proliferation was suppressed in the culture system using the collagen gel as compared with the conventional monolayer culture on plastic. Microcinematographically, this suppression was found to be due to an extension of the cell cycle time of each individual cell. On the other hand, there were no appreciable differences in proliferation pattern between the cells cultured on type I and IV collagen film and those cultured on plastic. These results suggest that there are interactions between type I collagen in the gel form and melanoma cells, especially with respect to cell growth.

Correlation of contractility and proliferative potential with the extent of differentiation in mouse fibroblastic cell lines cultured in collagen lattices.

Four types of fibroblastic cell lines at various stage of differentiation, which had been derived from syngeneic mice, were cultured in collagen lattices (reconstituted dermis model). Lattice contraction, growth in the lattice, and cell morphology were compared. The following cell lines were used: [I] precrisis cells within several subcultures derived from the skin of Balb/c mice, [II] an established normal cell line derived from syngeneic mice (Balb/3T3 clone A31), and [III] two transformed lines (Balb/3T12-3, 3T3-B-SV40) originating from [II]. The cells adopted a bipolar spindle form in the collagen lattice. Lattice contraction was the most marked with cell type [I] followed in order by [II] and [III]. Relative growth in the lattice occurred in the reverse order (III greater than II greater than I). These findings suggested a correlation between lattice contraction and growth in the lattice and also between the extent of differentiation and lattice contraction.

Enhanced melanogenesis of murine melanoma cells cultured on or in collagen gel.

To elucidate the interaction between melanoma and its matrix, we cultured B16 murine melanoma cells on and in type I collagen gel and evaluated specified functions of melanoma cells; tyrosinase activity and melanin-synthesizing capacity. Proliferation of cells cultured in these environments was markedly suppressed compared with that of cells cultured conventionally on plastic. On the other hand, the tyrosinase activity of cells cultured in or on collagen gel was two to three times higher than that of cells cultured on the plastics, while their melanin production was approximately double that achieved during conventional culture of cells. In conclusion, collagen gel influenced the growth and cell-specific functions of the melanoma cell. The culture system using collagen gel as substrate may be useful for the investigation of the interaction between melanoma and its matrix.

Contraction phenomenon of type I collagen gel by melanoma cells.

In order to study the interaction between melanoma cells and collagen, B16 murine melanoma cells were embedded and cultured in type I collagen gel. Melanoma cells cultured in the collagen gel became elongated, as compared with those cultured on plastic, and some of them assumed a dendritic form. The gel contracted very slowly but steadily during culturing of melanoma cells, as in the experiment using fibroblasts. On the 20th day of culture the area of the gel accounted for only 32% of that when culture started. This contraction was enhanced by retinoic acid, which is known to induce cell differentiation. The contractility of the gel differed between various lines of melanoma cells. The present observations raise the possibility of interaction between melanoma cells and type I collagen.

Correlation between ageing and collagen gel contractility of human fibroblasts.

To investigate the influence of ageing on wound healing, we cultured fibroblasts derived from human dermis in type I collagen gel, and evaluated the relationship between gel contractility and ageing. Cells were obtained from children (0-15 years old, Group A), early adulthood (16-40 years old, Group B), mid-adulthood (41-60 years old, Group C), and the elderly (61 or older, Group D). Gel contractility was determined by measuring the diameter on the second day after gel preparation. Within the tenth passage, gel contraction was the most marked in Group A, but did not differ among the other groups. Gel contraction at passages 30-40 did not differ from those within the tenth passage in Groups B, C and D, but it decreased markedly in Group A to a value similar to that in the other groups. These results show that fibroblasts in childhood are more contractile than those in adulthood and are more readily affected by passages (in vitro ageing).

Cell cycle analysis of human dermal fibroblasts cultured on or in hydrated type I collagen lattices.

The proliferation and cell cycle phase composition of human dermal fibroblasts cultured on or in type I collagen lattices (reconstituted dermis model) were examined. On collagen lattices, as compared with conventional cultures on plastic dishes, the proliferation of human dermal fibroblasts was suppressed, being arrested at about one-half the saturation density after 10 days of culture. In collagen lattices, proliferation was further suppressed, being nearly arrested within 4-7 days of culture. Cells were analyzed for cell cycle phases by two-color flow cytometry using DNA staining and S phase cell staining with FITC-conjugated antibromodeoxyuridine antibody. After 5 days of culture, the number of S phase cells on collagen lattices was 49.3% of that on plastic dishes, with an increase in G0G1 phase cells of 79.8%. In collagen lattices, the number of S phase cells was very small (4.3% of all cells), and most of the cells accumulated in G0G1 phase. These findings suggest that the cell cycle of fibroblasts is arrested at G0G1 phase by their interaction with collagen. On the basis of these results, the reconstituted dermis model using collagen lattice is considered to be analogous to the dermis in vivo with respect to cell growth and cell cycle phase composition.

Parallel arrangement, growth inhibition and cell cycle phase analysis of human dermal fibroblasts cultured in collagen lattice.

Human dermal fibroblasts were cultured in a hydrated type I collagen lattice. When collagen fibers were arranged in one direction, fibroblasts were arranged in the same direction. Cell proliferation was markedly suppressed in the collagen lattice as compared with that on plastic, with growth being arrested after day 5. No differences in proliferation were observed between aligned cells and randomly oriented cells. Flow cytometry with DNA staining was performed to analyze each phase of the cell cycle of fibroblasts. Among the 10,000 cell population, S phase cells on day 2 of culture accounted for 43% on plastic but were markedly inhibited to 25% in the lattice. On day 4, S phase cells accounted for 33% on plastic but only for 10% in the lattice. These findings suggest that cell advancement to the S phase is markedly inhibited in the collagen lattice, resulting in accumulation of most of cells in the G0G1 phase. The present study clearly showed that culture in the collagen lattice allowed alignment of fibroblasts with a definite orientation as observed in vivo and produced a status resembling that in vivo in terms of proliferation and cell cycle phase composition.