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Biomedical subjects

K Uenoyama

Publications and source records attributed to K Uenoyama.

At least 19 recordsLinked to original sources
PubMed1992

Re-evaluation of the biocompatibility of bioinert ceramics in vivo.

The affinity of bone for bioinert ceramics and stainless steel was compared using calcified bone specimens. We implanted cylinders of alumina ceramics (Al2O3), zirconia ceramics (ZrO2) and SUS-316 L stainless steel into the distal femoral epiphyses of dogs and then made observations from 4 to 96 wk post-operatively. Irregularities in the histological specimens suggested the presence of artefacts due to the insertion technique. We subsequently used screws inserted into holes tapped with a tap that had a diameter identical to the screws, and observed these implants from 4 to 96 wk after insertion. There was no detectable difference in the affinity index for all three materials from 4 to 96 wk after implantation. The affinity index was calculated as the ratio of the new bone directly adjoining the implant without any intervening fibrous membrane or bone marrow to the total length of the bone-implant interface x 100%.

Animals↗
PubMed1992

Collagenous deposits on explanted intraocular lenses.

An immunohistochemical study of type I collagen in deposits on the surface of two intraocular lenses (IOLs) explanted from human eyes was conducted. Type I collagen-immunoreactive proteinaceous deposits with cells were found around the haptics of an iris-supported IOL. A few such deposits and what appeared to be macrophages were observed on the optic. A few cells (presumably macrophages and giant cells) were observed on a posterior chamber IOL, whereas proteinaceous deposits that reacted positively to the antibody were not identified. Type I collagen-immunoreactive deposits on the iris-supported IOL were thought to be the products of fibroblastic cells, originating from iris tissue, that attached directly to the haptics and helped stabilize the implant.

Aged↗
PubMed1992

L-ascorbic acid 2-phosphate enhances the production of type I and type III collagen peptides in cultured rabbit keratocytes.

We studied the effect of L-ascorbic acid 2-phosphate (P-Asc), a long-acting phosphate derivative of L-ascorbic acid, on the production and secretion of type I and type III collagen peptides in cultured rabbit keratocytes using immunohistochemistry and enzyme immunoassay. P-Asc enhanced production and secretion of these collagen peptides. Our observations support a therapeutic role for P-Asc in the repair of corneal stromal damage such as caused by corneal chemical burn.

Animals↗
PubMed1992

[Implantation of IOLs with different diameters].

The intraocular lenses (IOLs) commonly used today are 13.5 to 14 mm in diameter, and this diameter is considered by some to be unnecessarily large. The size of the crystalline lens and the diagonal width between the ciliary sulcus were measured in rabbit eyes and human eyes. Then, IOLs with a smaller diameter (12.5 mm) were evaluated after implantation into rabbit eyes. The mean diameter of the human crystalline lens was 9.6 mm and its thickness was 4.1 mm. The mean width of the ciliary sulcus was 11.1 mm. The crystalline lenses of rabbits were larger than those of humans. Decentration and posterior capsular opacification score were 0.33 mm and 0.63 in 12.5 mm IOL, and 0.47 mm and 0.61 in 14.0 mm IOL. Indicating that the result of implanting the 12.5 mm IOL was not inferior to that of implanting the conventional 14 mm IOL. The average width of the ciliary sulcus is 11.1 mm, indicating that a 12.5 mm IOL is of a sufficient size to be firmly fixed in this sulcus. In addition, a 12.5 mm IOL is considered to be safer, because larger lenses may lead to erosion or vessel compression that could induce ischemia or neovascularization.

Animals↗
PubMed1992

Phagocytosis and fibronectin of cells observed on intraocular lenses.

The phagocytic activity and distribution of fibronectin in the cells adhering to implanted intraocular lenses (IOLs) were studied in rabbits. IOLs were explanted from the posterior chamber 7 days after implantation. Phagocytosis by the cells from the IOLs was studied by electron microscopy after incubation with polystyrene beads. The distribution of fibronectin was examined immunohistochemically using an anti-fibronectin antibody. Many presumed macrophages and giant cells which were thought to be of macrophagic origin were observed on the IOLs. Adherence of the beads to the surface of the cells, phagocytosis of these beads, and fibronectin immunoreactivity were prominent in these presumed macrophages, whereas giant cells displayed a reduction in these activities. These findings suggest that the adherence activities of the presumed macrophages are less after giant cells are formed, reflecting a reduced production of fibronectin.

Animals↗
PubMed1991

Quantitative analysis of in vivo tissue responses to titanium-oxide- and hydroxyapatite-coated titanium alloy.

We have previously studied a large number of histological specimens of biomaterials and found that regions with and without an intervening fibrous membrane coexisted in many specimens. Therefore, it appears necessary to perform an evaluation of the entire specimen when histologically assessing the affinity of bone for a biomaterial. Accordingly, we performed a quantitative histological evaluation of hydroxyapatite (HAP)- and titanium-oxide(TiO2)-coated Ti-6A1-4V and uncoated Ti-6A1-4V (control) by determining the affinity index. This was defined as the length of bone directly opposed to the implant/the total length of the bone-implant interface X 100%. The test materials were inserted into the distal epiphyseal region of the femurs of adult dogs, and follow-up quantitative histological comparisons were performed from 4 weeks to 96 weeks. The HAP-coated implants had the highest affinity index 4 weeks after insertion, and this superiority was maintained up to 96 weeks. There was a significant difference in affinity index between HAP-coated implants and control implants (P less than 0.001), while TiO2-coated implants showed no significant difference in comparison to the control.

Alloys↗
PubMed1991

L-ascorbic acid 2-phosphate, a phosphate derivative of L-ascorbic acid, enhances the growth of cultured rabbit keratocytes.

We examined the effect of L-ascorbic acid 2-phosphate (P-Asc) on the proliferation of cultured rabbit keratocytes. P-Asc is a phosphate derivative of L-ascorbic acid and has more prolonged vitamin C activity in solution than does L-ascorbic acid. The proliferation of cultured keratocytes was promoted by the presence of P-Asc in culture medium. Transmission electron microscopic observations revealed that cells were more multi-layered after culture in the presence of P-Asc (0.1 mM) for 30 days than were those cultured in the absence of P-Asc. The effect of P-Asc was abrogated by L-azetidine 2-carboxylic acid, which is an analogue of proline that inhibits the production and secretion of collagen. Our observations support a therapeutic role for P-Asc in the repair of corneal stromal damage such as that caused by a corneal chemical burn.

Animals↗
PubMed1991

[Effect of L-ascorbic acid 2-phosphate on cultured rabbit keratocytes (the third report). The effect on production and secretion of type I collagen].

We examined the effect of L-ascorbic acid 2-phosphate (P-Asc), a long-acting phosphate derivative of L-ascorbic acid, on intracellular distribution and production of type I collagen in cultured rabbit keratocytes by an immunohistochemistry and enzyme immunoassay. Exposure of 0.1 mM P-Asc for 10 hours decreased a type I collagen immunoreactivity of the cytoplasm as stained in fine granular materials. 0.1 mM P-Asc induced increase of type I collagen level in the medium. The results suggested that 0.1 mM P-Asc might increase the biosynthesis and secretion of type I collagen in keratocytes and have a therapeutic effect on corneal stromal damage.

Animals↗
PubMed1991

Immunohistochemical study of deposits on intraocular lenses explanted from human eyes.

Immunohistochemical studies of deposits were carried out on two intraocular lenses (IOLs) explanted from human eyes. One anterior chamber intraocular lens (AC-IOL) was studied using a monoclonal anti-human type I collagen-peptide antibody (C-Ab). One posterior chamber intraocular lens (PC-IOL) was studied using a monoclonal anti-human vimentin antibody (V-Ab). Most of the cells on the AC-IOL contained many melanin granules in the cytoplasm and were thought to be macrophages. They did not show any immunoreactivity to C-Ab. Some spindle-shaped cells and fibrous deposits at the margin of the lens optics showed immunoreactivity to the antibody. These cells were thought to be fibroblasts migrating from the tissue around the IOL, such as the iris. On the PC-IOL, many mononuclear cells and multinucleated giant cells were observed. These cells showed immunoreactivity to vimentin and contained immunostained fibers which were intermediate filaments. They were thought to be either of mesodermal origin or derived from the lens epithelium.

Aged↗
PubMed1991

[Effect of L-ascorbic acid 2-phosphate on cultured rabbit keratocytes (the second report)].

We examined the effect of L-ascorbic acid 2-phosphate (P-Asc) on the proliferation of cultured rabbit keratocytes. P-Asc is a derivative of L-ascorbic acid and it yields more prolonged effects of vitamin C in solution than L-ascorbic acid. The proliferation of cultured rabbit keratocytes was promoted by the presence of P-Asc in culture medium for 10, 20, and 30 days. Transmission electron microscopic observations revealed that the cells were more multilayered in the presence of P-Asc (0.1mM) for thirty days than those in the absence of P-Asc. Moreover, this effect of P-Asc was attenuated by azetidine 2-carboxylic acid which is an inhibitor of collagen synthesis. Hence, it is suggested that the promotive effect of P-Asc on the growth of cultured keratocytes is related to the synthesis of collagen. Based on our observations, P-Asc may have a therapeutic effect on corneal stromal damages such as a corneal chemical burn and surgical trauma.

Animals↗
PubMed1990

Experimental intraocular lens implantation in the rabbit eye and in the mouse peritoneal space. Part V: Phagocytosis and nuclear patterns of giant cells observed on the implanted lens surface.

The major cellular components on intraocular lenses experimentally implanted in the rabbit eye and in the mouse peritoneal space were examined. They consisted of macrophages and their metamorphosed epithelioid cells with occasional formations of foreign-body giant cells from the fusion of the macrophage-related cells. Lymphocytes, individually and in clusters, were also seen on the lenses implanted in the mouse peritoneal space but rarely on those implanted in the rabbit eye. Macrophages, epithelioid cells, and giant cells exhibited active phagocytosis on the implanted intraocular lenses. These cells phagocytized not only minor foreign particles such as artificially fed latex or carbon colloids but also living cells including erythrocytes, leukocytes, and lymphocytes. The nuclear pattern of the giant cell formation process initially assumed a centrally located nuclear distribution of a foreign-body giant cell type, and then a peripherally located Langhans type distribution when the number of nuclei reached about five in both the mouse peritoneal space and the rabbit eye chamber. Ultra-large giant cells containing a number of nuclei, however, were only observed on lenses implanted in the rabbit eye, demonstrating a difference between the two environments.

Animals↗
PubMed1990

Comparison of the cellular response on intraocular lenses implanted in rabbit eyes with and without extracapsular lens extraction.

Three-piece poly(methyl methacrylate) intraocular lenses (IOLs) were implanted in rabbit eyes with and without lens extraction to examine the cellular response on the IOL surface without the effects of the residual lens cortex. Each rabbit had extracapsular lens extraction (ECCE) with IOL implantation in the posterior chamber of one eye. In the second eye, the IOL was implanted in the anterior chamber without lens extraction. The lenses were removed and studied with light microscopy and scanning electron microscopy one week after surgery. Light microscopic findings revealed a similar cellular response on the surface of the IOLs in both groups. Scanning electron microscopy suggested that the cellular adhesiveness on the IOL surface in the eyes without lens extraction was weaker than in the eyes that had ECCE. Cells on the IOLs in the eyes without lens extraction were flatter and had membranous pseudopodia. It appears that the cells on the IOL surface were caused by a foreign body reaction and that their adhesiveness to the IOL was affected by residual lens cortex.

Animals↗
PubMed1989

Evaluation of metal implants coated with several types of ceramics as biomaterials.

The in vivo biocompatibility of metals coated with several different types of ceramics [alumina (alpha-Al2O3), titanium oxide (TiO2), titanium nitride (TiN), and hydroxyapatite (HAP)] was investigated. These composites had been devised for the purpose of incorporation into the stem of a total hip prosthesis. The materials were inserted into the mid-diaphyseal region of the femurs of adult dogs, and follow-up quantitative histological comparisons were performed for a period of up to 96 weeks. HAP-coated composites showed the best biocompatibility.

Aluminum Oxide↗
PubMed1989

The affinity of bone to hydroxyapatite and alumina in experimentally induced osteoporosis.

The authors studied how bone reacts to hydroxyapatite (HAP) and alumina (Al2O3) in osteoporosis experimentally induced in a rat animal model by resection of the sciatic nerve. Sixteen and 32 weeks after resection of the sciatic nerve, implants of HAP and Al2O3 were inserted into rat tibias. The reaction of bone to HAP was compared with its reaction to Al2O3, which is bioinert, as a control. The results were analyzed using the affinity index (the length of bone directly opposed to the implant without an intervening fibrous membrane/total length of the bone-implant interface x 100%). In the rats left for 16 weeks after resection of the sciatic nerve the index values 24 weeks after insertion of HAP and Al2O3 were 96.9 +/- 2.4% (N = 8) and 75.2 +/- 22.2% (N = 8), respectively. The index value of HAP was 97.2 +/- 2.6% (N = 12) and of Al2O3 was 86.9 +/- 15.4% (N = 12) at 24 weeks after insertion, when the rats were first left for 32 weeks, after sciatic nerve resection. Bone was demonstrated to have a superior affinity to HAP, compared with Al2O3 (P less than .05).

Aluminum↗
PubMed1989

Experimental intraocular lens implantation in the rabbit eye and in the mouse peritoneal space. Part IV: Cell adhesion, fibroblast-like cell, and lymphocytic cluster observed on the implanted lens surface.

Transmission and scanning electron microscopy, Wolter's implant cytology staining, and an immunohistochemical method were used to investigate the process of cell adhesion, the origin of fibroblast-like cells, and the nature of lymphocytic clusters that were observed on intraocular lenses (IOLs) experimentally implanted in the rabbit eye and in the mouse peritoneal space. On the IOL implanted in the mouse peritoneal space, pseudopodia extended during cell adhesion showed morphological variety; on the IOL implanted in the rabbit eye, membranous extensions were seen. Many of the fibroblast-like cells exhibited positive staining for macrophagic antigen, indicating a macrophagic origin. The build-up of lymphocytic clusters, as an indicator of immunologic activity, was frequently observed on IOLs implanted in the mouse peritoneal space, particularly on silicone IOLs. However, such clusters were rarely seen on poly(methyl methacrylate) or silicone IOLs implanted in the rabbit eye, suggesting a much reduced immune response to those materials in the eye chamber.

Animals↗
PubMed1989

[Experimental study of phagocytosis of the cells observed on the surface of intraocular lens].

It has been reported that macrophages adhere to implanted intraocular lens (IOL) in a reaction to the foreign body, and transform themselves into epithelioid cells, fibroblast-like cells, and foreign body giant cells. We attempted to examine the activity of these cells by studying phagocytosis. Extracapsular lens extractions with implantation of posterior chamber IOLs were performed in rabbit eyes. After one week, the implants were removed and incubated in culture medium containing latex beads to investigate phagocytosis of these cells adhering to the implants by light microscopy, scanning and transmission electron microscopy. The cells observed were macrophages, epithelioid cells, fibroblast-like cells, and foreign body giant cells. The round macrophage was most active in phagocytizing latex beads, while the activity was weaker in the epithelioid cells, fibroblast-like cells, and foreign body giant cells. The macrophages on the implants had many ruffles on their surface, and many latex beads adhered to the cell surface. The epithelioid cells and foreign body giant cells had few ruffles with few latex beads on their surface. These results suggested that cellular activity of the macrophages on the implanted IOL might decrease as their shape transformed.

Animals↗