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PubMed1996

Influence of the structure of three corals on their resorption kinetics.

The aim of this study was to investigate the influence of the structure of corals on their resorption kinetics after implantation in subcutaneous areas. Three types of coral (Porites astreoides, Montastrea annularis and Dichocoenia stokesi) identical in composition but different in structure were implanted for periods of 1 and 2 months in subcutaneous sites in OF1 mice. The resorption of the implants was studied by means of qualitative (histology, scanning electron microscopy, fluorochrome labelling method) and quantitative approaches (gravimetric method). The results of the qualitative study revealed a process of irregular deterioration of the coral, linked to the detachment of crystals at the surface of the implant. The results of the quantitative study showed that the speed of resorption increases with the implantation time and the open porosity of the coral. These reactions are explained by the increase of the surface exchange area in contact with factors responsible for resorption: biological medium and cells. When considering the choice of coral as a bone substitute, these factors must be taken into account to allow the in situ maintenance of the implant over a sufficiently long period of time according to the clinical situation.

Animals↗
PubMed1993

Bio-microscopical observation of dystrophic calcification induced by calcium hydroxide.

Calcium hydroxide paste was introduced into a rabbit ear chamber, and the effect of calcium hydroxide on the vascular tissue was observed under a bio-microscope continuously up to 14 weeks. Many precipitates were observed at the border of living tissue, after the dissolution of microvessels around the paste. They increased both in size and number to combine like a river bank in the first 48 h. After 1 week, microcirculation recovered, and newly-formed capillaries approached the precipitate-bank, the edge of which became smoother as weeks went by. The bank was stable and compatible to microvessels during the observation period. By SEM observation, the width of the bank was from 200 to 400 microns, and the tissue-side of the bank appeared like amorphous lamellae, while the inner-side showed particle-like appearance. EDX examination revealed high peaks of Ca and P similar to calcium phosphate at the tissue-side of the bank, but only Ca peak at the inner-side. The precipitates seemed to have the potential to induce dystrophic calcification by absorbing Ca and P from the tissue.

Animals↗
PubMed1997

Effect of XeCl-308nm excimer laser on the mineral content of human dentin.

The effect of the XeCl-308nm excimer laser on the mineral content and surface morphology of cut dentin was examined in ten extracted human teeth. Each dentin specimen was lased for 4 s at a fluence of 1 J/cm2 and a frequency of 25 Hz. Non-lased area of the same specimen served as control. Scanning electron microscopy and energy dispersive spectrometry revealed a significant decrease in the phosphorus levels following laser treatment. A decrease in calcium levels also occurred but was not statistically significant. Nonsignificant changes in sulphur and potassium levels were also noted. Morphologically, the lased dentin showed an apparently melted surface with partial obstruction of the dentin tubules as well as cracks along the lased surface. Therefore, it appeared that laser treatment may alter the chemical structure as well as the surface morphology of the dentin.

Calcium↗
PubMed2003

Resorbable and nonresorbable hydroxyapatite granules as bone graft substitutes in rabbit cortical defects.

BACKGROUND: The use of various synthetic calcium phosphate compositions for the promotion of bone in bone defects is of potential interest because such materials may be tailor made and may bond to bone. There is yet an inadequate knowledge of the role of calcium phosphate composition and resorbability for the bone response. PURPOSE: The aim of the present study was to compare the ability of resorbable versus nonresorbable hydroxyapatite (HA) granules to promote new bone formation in cortical bone defects. Resorbable and nonresorbable HA granules, used as bone graft substitutes, were evaluated after 6 weeks and 3 months in the rabbit tibia. Circular defects (diameter 5.0 mm) were made in both tibias of 18 New Zealand white rabbits. The 36 defects were divided into three groups (six observations per group and time, respectively). The first group was augmented with resorbable HA granules, the second group was augmented with ceramic nonresorbable HA granules, and the third group was left without augmentation (control). The animals were killed after 6 weeks and 3 months, and the tissue was evaluated with light microscopic (LM) morphology and morphometry, scanning electron microscopy (SEM), and energy dispersive x-ray analysis (EDX). RESULTS: After 3 months LM morphometry revealed significantly more newly formed bone in the two HA augmented groups compared with that in the control. A close contact was found between both kinds of HA granules and new bone as viewed with light microscopy and SEM. A relatively slow degradation process was indicated by the small reduction of the total granule area in the cortical defects. However, LM observations showed a change of granule form. Pilot experiments using SEM-EDX indicate that Ca and P contents had decreased in the resorbable HA granules between 6 weeks and 3 months. Further, a higher content of Ca and P was found in the newly formed bone close to granules, in comparison with more distant newly formed bone. CONCLUSIONS: Our results suggest that both resorbable and nonresorbable HA granules promote new bone formation in rabbit cortical defects, which does not occur in control defects.

Absorbable Implants↗
PubMed1984

Identification and quantitative analysis of tissue particulate burden.

The analysis of particles in tissue samples, especially in lung tissue samples, has been of great use diagnostically and in the search for more precise information on the etiology of occupational/environmental diseases. There is a strong need for an interdisciplinary approach involving patients, epidemiologists, clinicians, pathologists, toxicologists, and microscopists if advancement in the recognition, diagnosis, and prevention of disease is to proceed.

Asbestosis↗
PubMed1986

Analytical electron microscopy in the study of biological systems.

The AEM is a powerful tool in biological research, capable of providing information simply not available by other means. The use of a field emission STEM for this application can lead to a significant improvement in spatial resolution in most cases now allowed by the quality of the specimen preparation but perhaps ultimately limited by the effects of radiation damage. Increased elemental sensitivity is at least possible in selected cases with electron energy-loss spectrometry, but fundamental aspects of ELS will probably confine its role to that of a limited complement to EDS. The considerable margin for improvement in sensitivity of the basic analytical technique means that the search for technological improvement will continue. Fortunately, however, current technology can also continue to answer important biological questions.

Electricity↗
PubMed1994

The microtrephine. A new diagnostic tool for obtaining corneal biopsies.

We have developed a new tool for obtaining biopsies of the cornea in a manner which is less traumatic than former biopsy techniques. The new instrument consists of a drill with an aperture of 160 microns which functions as a trephine and is powered at 30,000 rpm. The instrument contains a 120 microns mandrel to remove the samples. In order to monitor electrolyte contents in alkali burnt corneas, 32 rabbit eyes underwent an alkali burn of one cornea (1 n NaOH for 30 sec) followed by a sequence of microtrephinations at different times. A total of 81 microtrephinations were performed. Fifty samples were obtained. One corneal perforation occurred. Forty-four puncture sites were examined by means of histology. Forty-eight biopsies were examined in a scanning electron microscope and identified as punctures of corneal tissue by way of an energy dispersive X-ray analysis. Human corneas had been punctured with this device.

Animals↗
PubMed2002

High abrasion resistance with sparse mineralization: copper biomineral in worm jaws.

Biominerals are widely exploited to harden or stiffen tissues in living organisms, with calcium-, silicon-, and iron-based minerals being most common. In notable contrast, the jaws of the marine bloodworm Glycera dibranchiata contain the copper-based biomineral atacamite [Cu2(OH)3Cl]. Polycrystalline fibers are oriented with the outer contour of the jaw. Using nanoindentation, we show that the mineral has a structural role and enhances hardness and stiffness. Despite the low degree of mineralization, bloodworm jaws exhibit an extraordinary resistance to abrasion, significantly exceeding that of vertebrate dentin and approaching that of tooth enamel.

Animals↗
PubMed1988

Breast tumors: composition of microcalcifications.

The authors investigated the crystallographic patterns of calcifications in breast tissue from 31 patients, including eight calcified benign lesions, 17 calcified carcinomas, and six noncalcified control samples. Scanning electron microscopy, energy-dispersive x-ray analysis, and x-ray diffraction with the Guinier camera were employed and yielded information on the shape and composition of breast calcifications. Polyhedral crystals (with energy-dispersive x-ray analysis response to calcium) contained calcite, aragonite, or calcium oxalate, depending on the case. Calcium oxalate crystals were found only in malignant breast tissues. Spherical crystals (with energy-dispersive x-ray analysis response to calcium and phosphorus) contained apatite. Spherical crystals predominated in malignant processes, but all shapes and compositions were present in both benign and malignant processes. The relationship of the calcification to its surrounding tissue may account for differences in structure, but results are inconclusive and require further study.

Breast↗
PubMed2007

Effect of ultraviolet B radiation on the absorption characteristics of various intraocular lenses.

BACKGROUND: The aim of this study was to determine the effect of ultraviolet B (UVB) exposure on UV filters of various intraocular lenses (IOLs). METHODS: Eight samples each of the hydrophobic acrylic, hydrophilic acrylic and silicone IOLs were used. Four IOLs of each type was selected randomly as the control group while the remaining four IOLs of each type were exposed to a UVB dose of 1.4 J/cm(2) (2.40 mW/cm(2)) for 9.45 min, two times with a 4-week interval. IOLs were evaluated for any sign of opacification under microscope weekly. After a follow-up period of 16 weeks, spectrometry for UV filter absorption rates, scanning electron microscopy for deposit formation and energy dispersive X-ray analysis for elemental composition were performed for all IOLs, and findings of the control group IOLs were compared with those of the UVB-exposed IOLs. All these procedures were done at the Department of Ophthalmology, Faculty of Medicine, Dokuz Eylul University. RESULTS: All the IOLs were free of any opacification during the follow-up period. Spectrometric analysis of their UV filters revealed a change in absorption rates in the hydrophilic acrylic and silicone IOLs compared to the control IOLs of the same type. Only the hydrophobic acrylic IOLs preserved the same UV absorption curve after UVB exposure. CONCLUSION: The pathogenesis of IOL opacification is still undetermined. Some reports claimed that the UV light was the responsible factor. Our experimental study revealed that high doses of UVB did not cause any opacification though they impaired the function of UV filters of the hydrophilic acrylic and silicone IOLs.

Acrylic Resins↗
PubMed1987

Zinc in the anterior pituitary of rat: a histochemical and analytical work.

Recent studies have suggested zinc to be a possible modulator of hormone secretion from the anterior pituitary. The three aims of the present study were: to estimate the total amount of zinc in the gland by instrumental analysis; to visualize the zinc at light and electron microscopical levels, and to estimate the amount of zinc that can be visualized by histochemical techniques. PIXE measurement showed the total amount of zinc to be 74 ng/mg dry weight in males and 100 ng/mg dry weight in females, which is a highly significant difference. Histochemically, the zinc was shown by a modified Timm method and the selenium method to be localized to the secretory granules, and to a smaller extent to the Golgi apparatus of the somatotrophs, corticotrophs and thyrotrophs. Chelation of tissue zinc by intravital dithizone treatment effectively blocked subsequent selenium and Timm staining in the secretory granules, and PIXE assays of the chelated metal (extracted into CCl4) showed it constituted less than 5% of the total zinc in the tissue. It is concluded from the study that zinc is present in the anterior pituitary of rats in rather high amounts and that loosely bound zinc, which is suggested to exert a biological effect by itself, can be located to the parts of the cells responsible for production, storing and release of hormones.

Animals↗