Biomedical subjects

F H Lin

Publications and source records attributed to F H Lin.

At least 37 records · Page 2Linked to original sources

PubMed1999

Thermal decomposition and reconstitution of hydroxyapatite in air atmosphere.

In this paper, the decomposition and reconstruction behavior of hydroxyapatite (HAP) during heating and cooling in air atmosphere were studied. The commercial HAP were chosen and gradually heated to 1500 degrees C and cooled to room temperature by a program controlled SiC heated furnace. X-ray diffraction (XRD) and Fourier-transformed infrared (FTIR) analysis were used to investigate the change of crystalline phases and functional groups of HAP at different temperatures. Weight change of samples was recorded by thermogravimetric analysis (TGA) during heating and cooling. The results revealed that HAP gradually releases its OH- ions and transforms into OHAP in the temperature of 1000-1360 degrees C. Above 1360 degrees C, the OHAP would decompose into TTCP and alpha TCP phase. The OH- stretching bands of HAP could be traced by FTIR even at the temperature of 1350 degrees C which indicates HAP decomposition. HAP does not dehydrate completely before decomposition. We speculated that some oxyapatite (OAP) might be formed during dehydration with a great amount of OHAP still left in the system even up to the temperature of decomposition. In the temperature range of 1400-1500 degrees C, there was no significant difference in XRD patterns, only TTCP and alpha TCP crystalline phases were observed. When the HAP gradually cools from 1500 degrees C, a part of TTCP and alpha TCP would directly reconstruct into OAP around 1350 degrees C. OAP existed in the temperature range of 1350-1300 degrees C during cooling. When the temperature decreased to 1290 degrees C, a part of TTCP and alpha TCP reconstructed into OHAP by rehydration reaction and OAP were rehydrated into OHAP as well. At 1100 degrees C, the rest of TTCP and alpha TCP reconstitutes into HAP. As the temperature decreases, the OHAP is gradually rehydrated and reconstituted into HAP.

Air↗

PubMed1999

The merit of sintered PDLLA/TCP composites in management of bone fracture internal fixation.

Polyesters based on lactic acid have been reported in terms of safety and biodegradation in human beings for 2 decades. The greatest advantage of such material is its degradation conducted only by hydrolysis, whereby the ester backbones are supposed to be unchained in the aqueous condition. The final degradable products are carbon dioxide and water which can be metabolized and digested in the physiological environment. The goal of this study was aimed at developing a composite sintered with poly-DL-lactide (PDLLA) and tricalcium phosphate (TCP) ceramic particles for orthopedic application. The TCP particles in a range of 30-60 wt% with 5 wt% increments were doped into the PDLLA matrix which was prepared by melting and hot pressing techniques for the reinforcement. The basic mechanical strength, biodegradable behavior, and biological response of the composites were investigated in the study. Various techniques such as pH meter, UV, Fourier-transform infrared, and x-ray diffractometer were used to examine and record the degradable process of the composites soaked in saline for 1-16 weeks. The rabbit femur condyle fracture fixation test was used to evaluate tissue compatibility and the effects of bone fracture fixation on the composites. Histological observation and x-ray photography were used for investigating assistance. The mechanical strength of the composites initially increased with TCP additions up to 50wt%, but thereafter they showed no significant difference (p < 0.05). The composite with 50 wt% TCP addition showed greater mechanical strength and had good agreement with cortical bone in terms of its elastic modulus of 30-40 GPa. The weight loss of the pure PDLLA soaked in the saline started at 4 weeks and reached 95% after 16 weeks. The composites compared with pure PDLLA, however, showed no apparent evidence of degradation after soaked for 12 weeks. The possible mechanisms for the delayed degradation of the composites in saline might have been solution penetration retardation by the ceramic particles and chemical bonds formed between the interface of the TCP particles and the PDLLA matrix. In the histological evaluation of the rabbit femur condyle fracture fixation test, the surface of the composite with 50 wt% TCP addition was attached by the newly generated bone without fibrous tissue around 8 weeks after implantation. The fractured bone was gradually healed and the composite firmly and properly fixed on the fracture area during the implanted period, which provided a breeding environment for normal bone remodeling. The developed composite was thought to be an alternative material for orthopedic application in the future, especially for bone screws and bone plates.

Absorption↗

PubMed1999

The effect of sintered beta-dicalcium pyrophosphate particle size on newborn Wistar rat osteoblasts.

During recent years, sintered dicalcium phosphate (SDCP) has been shown to be an effective artificial bone filler for repairing bone defects. The goal of this study was to elucidate the effect of SDCP particle size on osteoblasts. Osteoblasts were mixed and cultured with various sized SDCP particles (0.5-3.0, 37-63, 177-250, and 420-841 microns) for 1 h, 3 h, 1 day, 3 days, and 7 days and then analyzed. The results show that the adding of smaller sized SDCP particles (0.5-3.0 and 37-63 microns) into osteoblast culture can significantly affect the cell counts of osteoblasts. The secretion of transforming growth factor-beta 1, alkaline phosphatase, and prostaglandin E2 in culture medium increased significantly. The changes were most significant and persisted longer in smaller particle groups. Small sintered dicalcium phosphate particles can inhibit the proliferation of the osteoblasts. The inhibitory effects of the smaller sized SDCP particles on the osteoblasts were mediated by the promotion of osteoblast differentiation and the increased synthesis of prostaglandin E2.

Alkaline Phosphatase↗

PubMed1999

Quantitative spectral/spatial analysis of phased array coil in magnetic resonance imaging based on method of moment.

A new approach for analysis of RF coils in magnetic resonance (MR) experiments is reported. Instead of assuming current distribution in conventional quasi-static algorithm, this approach transforms the coil geometry into an equivalent circuit for complex current calculation. Self and mutual inductance are taken into consideration. Frequency responses of RF coils and transverse magnetic field (B1) maps can be simulated. This approach is especially efficient for phased array coil design for its small matrix size when implemented on computers. Experiments on both single surface coil and phased array coils are consistent with simulation results. Index Terms-Magnetic resonance, method of moment, phased array coil, RF coil.

Algorithms↗

PubMed1999

Cytokine and prostaglandin E2 release from leukocytes in response to metal ions derived from different prosthetic materials: an in vitro study.

Cytokines produced by leukocytes in the periprosthetic membranes surrounding joint replacements have been implicated as causal agents in osteolysis and prosthetic loosening. In this study, we used an in vitro leukocyte culture system to monitor the response of leukocytes to various metal ions and their possible roles in the mechanism of aseptic loosening. Human peripheral leukocytes were isolated and incubated with various concentrations of Co2+, Cr3+, and Ti3+ ions. Leukocyte cell counts and the levels of the tumor necrosis factor-alpha (TNF-alpha), interleukin-1 (IL-1), interleukin-6 (IL-6) and prostaglandin E2 (PGE2) released into the media were analyzed at 1 h, 3 h, and 1, 3, and 7 day intervals. The results showed that adding different metal ions into leukocyte cultures did not affect the cell counts. Exposure of leukocytes to Co2+ ion increased the release of TNF-alpha, IL-6, and PGE2. Exposure of leukocytes to Cr3+ ion did not increase the release of TNF-alpha but increased the secretion of IL-6 and PGE2. In contrast, exposure of the leukocytes to Ti3+ ions was associated with a decrease in the release of TNF-alpha and PGE2 and a minimal change in IL-6 noted after 7 days' culture. The present study elucidated the possible mechanisms involved in periprosthetic osteolysis and the inflammatory response of human leukocytes to metal ions. We found that cobalt ion is the most potent stimulant for cytokines and prostaglandin secretion by leukocytes. This elucidation, in combination with other efforts to reduce the generation of wear debris and metal ions, may improve the longevity of orthopedic implants.

Cell Count↗

PubMed1999

Studies of the lethargic (lh/lh) mouse model of absence seizures: regulatory mechanisms and identification of the lh gene.

To understand the cellular and molecular mechanisms that underlie generalized absence seizures sufficiently well to design rational, efficacious new therapies for patients, it is necessary to turn to animal models to gain insights into these mechanisms. The lethargic (lh/lh) mutant mouse expresses spontaneous absence seizures that share behavioral, electrographic, and anticonvulsant profiles with absence seizures in patients. This validates its use to study the mechanisms that underlie absence seizures. This chapter discusses two scientific approaches that involve the use of lh/lh mice. The first part of the chapter discusses neurobiologic approaches used to investigate critical mechanisms that regulate the synchronized burst firing within the thalamocortical network that generates absence seizures. Two of these critical mechanisms have been studied in detail with lh/lh mice. The first critical mechanism involves the required activation of gamma-aminobutyric acid B (GABAB) receptors to generate absence seizures. Because the numbers of GABAB receptors are increased in thalamocortical populations among lh/lh mice compared with littermates without epilepsy, these receptors appear to play a pathophysiologic role in the expression of absence seizures among lh/lh mice. Moreover, there may be a role for GABAB receptors in the generation of absence seizures among humans, because administration of compounds that activate GABAB receptors can produce absence seizures among humans. These findings suggest that GABAB receptor antagonists may represent a new class of antiabsence compounds that will be efficacious against absence seizures among patients. A second critical mechanism that regulates generation of absence seizures involves GABAA receptors in the nucleus reticularis thalami (NRT), a nucleus that sends GABA-ergic afferents to thalamic relay nuclei. Activation of GABAA receptors in the NRT appears to suppress the generation of absence seizures among lh/lh mice and in other models. Moreover, clonazepam may exert its antiabsence actions through this mechanism. Together, these findings suggest that compounds that selectively activate GABAA receptor isoforms expressed in NRT may represent a class of antiabsence drugs that could have fewer side effects than compounds currently used to treat patients. The second part of the chapter discusses a molecular genetic approach to delineation of the mechanisms that underlie absence seizures. Absence seizures among lh/lh mice are caused by a single-gene defect on chromosome 2. If positional cloning and gene isolation techniques are successful, it will be possible to identify the lh disease gene. Subsequent studies of the lh gene product should greatly increase not only our understanding of the pathophysiologic basis for absence seizures among lh/lh mice but also our ability to seek similar mutations in homologous genes in human families that express absence seizures. Accordingly, strategies and progress in cloning and identifying the lh disease gene are presented.

Animals↗

PubMed1999

Treatment of dental root fracture by medium energy CO2 laser and DP-bioactive glass paste. Part. II: Compositional, structure, and phase changes of DP-bioglass paste after exposed to CO2 laser.

Fractured teeth are difficult to treat effectively. Currently, such as root fractures are usually treated by full-coverage restoration, root amputation, or tooth extraction. If the fusion of tooth fracture by laser were possible, it could offer a different therapy to repair fracture teeth. We tried to use a developed DP-bioactive glass paste to fuse or bridge the tooth crack line by a medium energy continuous-wave CO2 laser. The present report was focused on the phase transformation and rescrystallization of DP-bioactive paste during expose to the CO2 laser. The materials will examine by means of XRD, FTIR, DTA/TGA, and SEM. From the study, we could expect that the temperature increase due to laser irradiation must be over than 900 degrees C and the DP-bioactive glass paste could be melted in a short period of time after irradiation. In the study, we successfully developed a DP-bioactive glass paste which could form a melting glass within minutes after exposed to a medium energy density continuous-wave CO2 laser. The paste will be used to bridge the enamel or dentine surface crack by the continuous-wave CO2 laser in the near future.

Dental Cements↗

PubMed1999

Thermal decomposition and reconstruction of hydroxyapatite in air atmosphere.

In this paper, the decomposition and reconstruction behavior of hydroxyapatite (HAP) during heating and cooling in air atmosphere were studied. The commercial HAP were chosen and gradually heated to 1500 degrees C and cooled to room temperature by a program controlled SiC heated furnace. X-ray diffractometer (XRD) and Fourier-transformed infrared (FTIR) analysis were used to investigate the change of crystalline phases and functional groups of HAP at different temperatures. Weight change of samples was recorded by thermogravimetric analysis (TGA) during heating and cooling. The results revealed that HAP would gradually release its OH- ions and transform into OHAP in the temperature of 1000-1360 degrees C. Above 1360 degrees C, the OHAP would decompose into TTCP and alpha TCP phase. The OH- stretching bands of HAP could be traced by FTIR even at the temperature of 1350 degrees C which was the eve of HAP decomposition. It reflected that the HAP did not dehydrate completely before decomposed. We speculated that some of OAP might be formed during dehydration and there were a great amount of OHAP still left in the system even up to the temperature of decomposition. In the temperature of 1400-1500 degrees C, there were no significant different in XRD patterns, only TTCP and alpha TCP crystalline phase were observed. When the HAP gradually cooled down from 1500 degrees C, a part of TTCP and alpha TCP would directly reconstruct into oxyapatite (OAP) around 1350 degrees C. OAP existed in the temperature of 1350 to 1300 degrees C during cooling. When the temperature down to 1290 degrees C, a part of TTCP and alpha TCP reconstructed into OHAP by rehydration reaction and OAP were rehydrated into OHAP as well. At 1100 degrees C, the rest of TTCP and alpha TCP would reconstitute into HAP. As the temperature decreased, the OHAP were gradually rehydrated and reconstituted into HAP.

Biocompatible Materials↗

PubMed1998

Influence of hydroxyapatite particle size on bone cell activities: an in vitro study.

Over the past decade, a large number of biomaterials have been proposed as artificial bone fillers for repairing bone defects. The material most widely used in clinical medicine is hydroxyapatite. The aim of our investigation was to study the effect of hydroxyapatite size mechanism on osteoblasts. The osteoblasts were cultured in vitro with 0.1% (1 mg/mL) of various sized hydroxyapatite particles (0.5-3.0, 37-63, 177-250, and 420-841 microm) for 1 h, 3 h, 1 day, 3 days, and 7 days. The results showed that adding hydroxyapatite particles to osteoblast cultures can significantly affect osteoblast cell count. Osteoblast populations decreased significantly. Osteoblast mean surface areas also changed significantly. Transforming growth factor-beta1 (TGF-beta1) concentrations in culture medium decreased significantly with the addition of hydroxyapatite particles. Prostaglandin E2 (PGE2) concentrations in medium increased significantly. The changes in TGF-beta1 and PGE2 concentration were more significant and persisted longer in smaller-particle groups. The inhibitory effects of hydroxyapatite particles on osteoblast cell cultures were mediated by the increased synthesis of PGE2. Caution should be exercised before using a hydroxyapatite product which could easily break down into fine particles.

Alkaline Phosphatase↗

PubMed1998

Biological effects and cytotoxicity of the composite composed by tricalcium phosphate and glutaraldehyde cross-linked gelatin.

The purpose of this study was to prepare and evaluate the feasibility and cytocompatibility of a composite (GTG) as a large defect bone substitute. The composite is combined with tricalcium phosphate ceramic particles and glutaraldehyde cross-linked gelatin. Gelatin had been reported as an adhesive and biocompatible binder that could accelerate the recovery of damaged soft tissue, but the effects of gelatin when acting on the bone tissue is not clear. Thus, it is necessary to determine if the substances released from the GTG composite can facilitate the growth of bone cells. The substances released from the GTG composites after being soaked in deionized distilled water were analyzed by gas chromatography (GC), ultraviolet and visible absorption spectroscopy (UV-VIS), and inductive-coupled plasma-atomic emission spectrometry (ICP-AES). The cytotoxicity of the GTG composites was assessed by coculture of rat osteoblasts in vitro. Extracts were obtained by soaking the GTG composites in deionized distilled water for 1, 2, 4, 7, 14, 28 and 42 d. The extract mixed with complete medium in a ratio of 1:1 was added into the cell culture wells containing 1 x 10(4) cells ml(-1) osteoblasts. After culturing for 2 days, the cells attached to the surface of wells were trypsinized and the number calculated by the Neubauer counting-chamber under the optical microscope. Finally, three samples in each GTG group were examined by scanning electron microscopy (SEM) to observe the morphology of the osteoblasts attached to the surfaces of GTG composites. The examinations of osteoblasts cocultured with the developed GTG composites were used to decide the ideal concentration of glutaraldehyde as a cross-linking agent. The results of extracts cocultured with osteoblasts showed that the extracts obtained from the 2, 4 and 8% glutaraldehyde cross-linked GTG composites would inhibit the growth of osteoblasts in the first 4 soaking days. During the 4-7 days soaking, the cell numbers quickly increased with the soaking time, thereafter, the cell numbers almost reached a constant value. In the analyses of substances released from the GTG composites, it was found that the gelatin and calcium were gradually released from the GTG composites, which were supposed to be nutritious for the growth of the osteoblast. The results of osteoblasts cocultured with the GTG composites showed that the concentration of glutaraldehyde used as a cross-linking agent should be lower than 8%. Compared to the GTF (composite combined with tricalcium phosphate ceramic particles and formaldehyde cross-linked gelatin), GTG composites were much suitable for a large defect bone substitute in the near future.

Animals↗

PubMed1998

Preparation of high-temperature stabilized beta-tricalcium phosphate by heating deficient hydroxyapatite with Na4P2O7 x 10H2O addition.

In this paper, the high-temperature stabilized beta-tricalcium phosphate (betaTCP, beta-Ca3(PO4)2) were prepared by heating the deficient HAP (d-HAP, Ca10-x(HPO4)x(PO4)6-x(OH)2-x) with tetra-sodium diphosphate decahydrate (NP, Na4P2O7 x 10H2O) addition. The betaTCP, d-HAP and d-HAP doped with 2.5, 5, 7.5 and 10 wt % NP were heated to different temperatures and were investigated by X-ray diffraction analysis (XRD) and Fourier-transformed infrared spectroscopy (FTIR). The results demonstrated that the HPO4(2-) of d-HAP condensed into P2O7(4-) occurred before 650 degrees C. The P2O7(4-) ions could be traced in the FTIR spectrum when the d-HAP was heated up to 750 degrees C. The reaction of P2O7(4-) with OH- did not occur instantly but over a wide range of temperatures. The d-HAP doped with NP would decrease the decomposition temperature of d-HAP. NP doped into d-HAP not only induced the d-HAP decomposition at lower temperature but also stabilized the betaTCP crystal structure at higher-temperature. It could also increase the conversion temperature of betaTCP to alphaTCP from 1180 degrees C up to 1300 degrees C. We could successfully prepare high-temperature (up to 1300 C) stabilized ffTCP by heating NP doped d-HAP.

Calcium Phosphates↗

PubMed1997

The effects of calcium phosphate particles on the growth of osteoblasts.

With advances in ceramics technology, calcium phosphate bioceramics have been applied as bone substitutes for several decades. The focus of this work is to elucidate the biocompatibility of the particulates of various calcium phosphate cytotoxicities. Four different kinds of calcium phosphate powders, including beta-tricalcium phosphate (beta-TCP), hydroxyapatite (HA), beta-dicalcium pyrophosphate (beta-DCP), and sintered beta-dicalcium pyrophosphate (SDCP), were tested by osteoblast cell culture. The results were analyzed by cell count, concentration of transforming growth factor-beta 1 (TGF-beta 1), alkaline phosphatase (ALP), and prostaglandin E2 (PGE2) in culture media. The changes were most significant when osteoblasts were cultured with beta-TCP and HA bioceramics. The changes in cell population of the beta-TCP and HA were quite low in the first 3 days, then increased gradually toward the seventh day. The changes in TGF-beta 1 concentration in culture medium inversely related to the changes in cell population. The ALP titer in the culture media of the beta-TCP and HA were quite high in the first 3 days, then decreased rapidly between the third and seventh days. The concentrations of PGE2 in the culture media tested were quite high on the first day, decreased rapidly to the third day, and then gradually until the seventh day. The changes in the beta-DCP and SDCP were quite similar to those of HA and beta-TCP but much less significant. We conclude that HA and beta-TCP have an inhibitory effect on the growth of osteoblasts. The inhibitins effects of the HA and beta-TCP powders on the osteoblast cell cultures possibly are mediated by the increased synthesis of PGE2.

Alkaline Phosphatase↗

PubMed1997

In vitro cell behavior of osteoblasts on Pyrost bone substitute.

BACKGROUND: Pyrost bone substitute has been shown to be a promising orthopedic biomaterial. However, little is known about mechanisms that are responsible for the genesis and development of the bond between bone and the Pyrost bone substitute. The purpose of this study is to elucidate the in vitro cell behavior of osteoblasts on Pyrost bone substitute. METHODS: By using primary culture of rat osteoblasts, the changes in cell morphology during adhesion and flattening onto the surface of Pyrost bone substitute were studied in vitro. At 1 hour, at 3 hours, and at days 1, 3, and 7 after layering, the cell behavior was observed with scanning electron microscope. RESULTS: The processes of trypsinized osteoblast adhesion and spreading on Pyrost bone substitute consisted of 1) contact of rounded osteoblasts with the Pyrost substrate; 2) attachment of osteoblasts at point of contact; 3) centrifugal growth of filopodia; 4) flattening and spreading of the osteoblasts on the Pyrost substrate; 5) division and growth of osteoblasts; and 6) suspension of the osteoblasts across the pores by their processes. CONCLUSIONS: These results demonstrated that Pyrost can form a physico-chemical bond with osteoblasts. The Pyrost bone substitute not only supports osteoblasts attachment but also allows proliferation of the osteoblasts.

Animals↗

PubMed1997

Effects of calcium phosphate bioceramics on skeletal muscle cells.

With advances in ceramics technology, calcium phosphate bioceramics have been applied as bone substitutes. The effects of implants on bony tissue have been investigated. The effects upon adjacent skeletal muscles have not been determined. The focus of this work is to elucidate the biological effects of various calcium phosphate bioceramics on skeletal muscles. Four different kinds of powder of calcium phosphate biomaterials including beta-tricalcium phosphate (beta-TCP), hydroxyapatite (HA), beta-dicalcium pyrophosphate (beta-DCP) and sintered beta-dicalcium pyrophosphate (SDCP), were tested by myoblast cell cultures. The results were analyzed by cell count, cell morphology and concentration of transforming growth factor beta 1 (TGF-beta 1) in culture medium. The cell population and TGF-beta 1 concentration of the control sample increased persistently as the time of culture increased. The changes in cell population and TGF-beta 1 concentration in culture medium of the beta-TCP and HA were quite low in the first 3 days of culture, then increased gradually toward the seventh day. The changes in cell population and TGF-beta 1 concentration in culture medium of the silica, beta-DCP, and SDCP were quite similar. They were lower during the first day of culture but increased and reached that of the control medium after 7 days' culture. Most cells on B-TCP and HA diminished in size with radially spread, long pseudopods. We conclude that HA and beta-TCP are thought to have an inhibitory effect on growth of the myoblasts. The HA and beta-TCP may interfere with the repair and regeneration of injured skeletal muscle after orthopedic surgery.

Animals↗

PubMed1997

Effect of hydroxyapatite particle size on myoblasts and fibroblasts.

After surgery, the bone and soft tissues around integrated biomaterials can be adversely affected by implant-related factors acting over a period of years. However, few studies have directly addressed the effects upon the adjacent soft tissue. The present study was designed to test the biological effects of various sized hydroxyapatite (HA) particles on myoblasts and fibroblasts. Both the myoblasts and fibroblasts were mixed in in vitro culture with 0.1% (1 mg ml(-1)) of various sized HA particles (0.5-3.0, 37-63, 177-250, 420-841 microm) for 1 h, 3 h, 1 day, 3 days and 7 days to test their effects on the cell culture. The results show that adding HA particles into a cell culture can decrease the cell count significantly. The transforming growth factor-beta1 (TGF-beta1) concentrations in the culture medium decreased significantly on addition of HA particles. When calculated as a ratio to the cell number, the TGF-beta1 titre increased most significantly in the groups of medium-sized particles. The prostaglandin E2 (PGE2) concentrations in the medium increased significantly. The changes in TGF-beta1 and PGE2 concentrations with the smallest particles were most significant and persisted longer. The inhibitory effects of the HA particles on the cell culture were mediated by the increased synthesis of PGE2. Caution should be exercised before considering the use of an HA product which could easily break down into a fine powder.

Animals↗

PubMed1997

Degradation behaviour of a new bioceramic: Ca2P2O7 with addition of Na4P2O7.10H2O.

A newly produced bioceramic, beta-Ca2P2O7 with addition of Na4P2O7.10H2O (SDCP), has been implanted into the femoral condyle of rabbits. Within 6 weeks after implantation, most of the bioceramic is replaced by new woven bone. On the contrary, block from hydroxyapatite (HA) and beta-tricalcium phosphate (beta-TCP), which are osteoconductible, do not resorb within a short period of time. We believe that the biodegradable behaviour of SDCP may occur in two steps. The first and most important step is the digestion of particles and migration of the particles by phagocytosis. The object of this study is to examine the change in morphologies, chemical compositions and crystal structure of SDCP after soaking in distilled water for a certain period of time. The SDCP ceramic was also co-cultured with leucocytes to observe how the SDCP particles were digested by the leucocytes, so that the mechanism of biodegradable behaviour of SDCP ceramic in vivo might be clarified. Four types of sintered calcium phosphate ceramics were tested in the experiment: SDCP, pure beta-Ca2P2O7 (DCP), HA and beta-TCP. They wee soaked in distilled water at 37 degrees C for up to 30 days. The microstructure and morphology of crystals deposited on the surface were observed using scanning electron microscopy. Sodium, calcium and phosphorus ion contents in the supernatant solution were detected by atomic absorption analysis and ion coupled plasma. In summary, HA and DCP showed no significant evidence of dissolution in distilled water. In static distilled water, calcium ions may be released from beta-TCP into solution during the initial 7 days and then converted into HA by reprecipitation. The results showed that the SDCP was firstly dissolved into small grains or fragments by the solution. The small fragments should be so small as to be digested by the phagocytes in a physiological environment.

Animals↗

PubMed1997

Biocompatibility and osteoconductivity of the pyrost bone substitutes.

The purpose of this study was to re-evaluate the bone regeneration power and the in vitro biocompatibility of the Pyrost bone substitute. Twenty-four adult New Zealand White rabbits were used. Bony defect over both iliac crest and mid-diaphyseal portion of the ulna bone were created. Appropriate sized-block of Pyrost bone substitute were implanted. Four of the animals were killed at each postoperative month to evaluate its bone regeneration power by histologic study. The Pyrost bones were co-cultured with osteoblasts to evaluate its biocompatibility. The results showed that Pyrost bone substitute was quite stable and incorporated well with active bone regeneration. The Pyrost heal better at the iliac crest than at the ulnar defect. The Pyrost was compatible to the osteoblasts. Osteoblasts had successfully seeded and mitotically expanded on the porous surface of the Pyrost bone graft. The result showed that Pyrost bone obviously exerts an intense stimulus on osteo-regeneration in the presence of osteoblasts. We consider Pyrost to be an alternate to the conventional preserved allografts that is occasionally necessary.

Animals↗

PubMed1997

Generalized epilepsies: emerging insights into cellular and genetic mechanisms.

In the past year we have gained significant insights into the molecular and genetic mechanisms underlying generalized absence seizures, primarily through the study of animal models. Also a new understanding has emerged about the genetic bases of certain syndromes in which generalized myoclonic and tonic-clonic seizures are expressed. New insights into these different types of generalized seizures may lead eventually to new therapies.

Animals↗