Biomedical subjects

J A Jansen

Publications and source records attributed to J A Jansen.

At least 145 records · Page 8Linked to original sources

PubMed1996

Quantitative analysis of cell proliferation and orientation on substrata with uniform parallel surface micro-grooves.

In order to quantify the effect of the substrata surface topography on cellular behaviour, planar and micro-textured silicon substrata were produced and made suitable for cell culture by radio frequency glow discharge treatment. These substrata possessed parallel surface grooves with a groove and ridge width of 2.0 (SilD02), 5.0 (SilD05) and 10 microns (SilD10). Groove depth was approximately 0.5 micron. Rat dermal fibroblasts (RDFs) were cultured on these substrata and a tissue culture polystyrene control surface for 1, 2, 3, 5 and 7 days. After incubation the cell proliferation was quantified with a Coulter Counter, and RDF size, shape and orientation with digital image analysis. Cell counts proved that neither the presence of the surface grooves nor the dimension of these grooves had an effect on the cell proliferation. However, RDFs on SilD02, and to a lesser extent on SilD05 substrata, were elongated and aligned parallel to the surface grooves. Orientation of the RDFs on SilD10 substrata proved to be almost comparable to the SilD00 substrata. Finally, it was observed that the cells on the micro-textured substrata were capable of spanning the surface grooves.

Animals↗

PubMed1996

Influence of annealing temperature on RF magnetron sputtered calcium phosphate coatings.

The effect of different annealing temperatures on the characteristics of thin calcium phosphate coatings fabricated by radiofrequency magnetron sputtering was studied. Annealing of the as-sputtered films was necessary to change the amorphous coating to a crystalline coating. The films were annealed for 2 and 4 h at 400, 600, 800, 1000 and 1200 degrees C under dry argon or argon and water vapour flow. After annealing, the structure and the chemical composition of these films were characterized with incident light microscopy, Rutherford backscattering spectrometry (RBS), X-ray diffraction (XRD), and Fourier transform infrared absorption spectrometry (FTIR). Incident light microscopy showed cracks in the coatings annealed at a higher temperature than 400 degrees C. RBS revealed that the as-sputtered coatings had a high Ca/P ratio which decreased with increasing annealing temperature. After annealing at a temperature of 600 degrees C or more the XRD showed crystalline hydroxyapatite (HA) coatings. However, the second phase, present in the coatings, changed from tetra-calcium phosphate to calcium oxide to beta-tri-calcium phosphate with increasing annealing temperature. FTIR measurements showed the existence of OH- and PO- bonds in all coatings, although the PO- bonds varied for different annealed coatings, from the PO- bonds due to HA to PO- bonds due to other calcium phosphates. From the results of this study we suggest that 600 degrees C is probably the best annealing temperature to obtain a better characterization and understanding of the coating.

Biocompatible Materials↗

PubMed1995

Influence of discharge power level on the properties of hydroxyapatite films deposited on Ti6A14V with RF magnetron sputtering.

The effects of discharge radiofrequency (RF) power and film thickness were studied on the characteristics of Ca5(PO4)3OH (hydroxyapatite) thin films fabricated by RF magnetron sputtering. The structure and chemical composition were investigated with alpha-step (thickness), scanning electron microscopy (SEM), X-ray diffraction (XRD), Rutherford backscattering spectrometry (RBS), and infrared absorption spectrometry (FTIR). The films were analyzed as-sputtered and after annealing at 550 degrees C under argon flow. SEM showed that the film surfaces had no cracks or other defects. X-ray diffraction showed that the deposited films were amorphous with low-discharge RF power, and crystalline with high-discharge RF power. After annealing, all the films had the same crystalline structure as apatite. However, the RBS measurements revealed that all films had a higher calcium-phosphate ratio than standard synthetic hydroxyapatite. Furthermore, statistical testing of the RBS data revealed the existence of only a weak correlation between the Ca/P ratio and the discharge power level. Although all sputtered films showed phosphate bonds in the infrared spectrum, only after annealing did the OH bonds of hydroxyapatite become visible.

Alloys↗

PubMed1995

Effect of parallel surface microgrooves and surface energy on cell growth.

To evaluate the effect of surface treatment and surface microtexture on cellular behavior, smooth and microtextured silicone substrata were produced. The microtextured substrata possessed parallel surface grooves with a width and spacing of 2.0 (SilD02), 5.0 (SilD05), and 10 microns (SilD10). The groove depth was approximately 0.5 microns. Subsequently, these substrata were either left untreated (NT) or treated by ultraviolet irradiation (UV), radiofrequency glow discharge treatment (RFGD), or both (UVRFGD). After characterization of the substrata, rat dermal fibroblasts (RDF) were cultured on the UV, RFGD, and UVRFGD treated surfaces for 1, 3, 5, and 7 days. Comparison between the NT and UV substrata revealed that UV treatment did not influence the contact angles and surface energies of surfaces with a similar surface topography. However, the contact angles of the RFGD and UVRFGD substrata were significantly smaller than those of the UV and NT substrata. The dimension of the surface microevents did not influence the wettability characteristics. Cell culture experiments revealed that RDF cell growth on UV-treated surfaces was lower than on the RFGD and UVRFGD substrata. SEM examination demonstrated that the parallel surface grooves on the SilD02 and SilD05 substrata were able to induce stronger cell orientation and alignment than the events on SilD10 surfaces. By combining all of our findings, the most important conclusion was that physicochemical parameters such as wettability and surface free energy influence cell growth but play no measurable role in the shape and orientation of cells on microtextured surfaces.

Animals↗

PubMed1995

Biological evaluation of the effect of magnetron sputtered Ca/P coatings on osteoblast-like cells in vitro.

A rat bone marrow cell culture was used to evaluate the osteogenic potential of amorphous and crystalline thin calcium phosphate (Ca/P) coatings. The coatings were deposited on titanium discs using a radiofrequency magnetron sputter procedure. Amorphous and crystalline plasma spray Ca/P coated and noncoated titanium discs served as reference material. The cellular behavior was analyzed with quantitative (attachment and proliferation rates) and qualitative (scanning electron microscopy) techniques. No significant differences were found in cell attachment and proliferation rates between the various materials. Scanning electron microscopy showed extracellular matrix formation after 18 days of culture on amorphous plasma-sprayed and the two types of magnetron sputtered coatings. Furthermore, no severe degradation of the magnetron sputtered coatings was observed. They even appeared to induce apatite formation. On basis of the results, we conclude that magnetron sputtering appears to be a promising method to manufacture bioactive ceramic coatings.

Animals↗

PubMed1995

Effect of calcium phosphate (Ca-P) coatings on trabecular bone response: a histological study.

The trabecular bone response to noncoated and fluorapatite (FA), hydroxyapatite (HA), and hydroxyapatite heat-treated (HAHT) plasma-sprayed coated implants was investigated in a goat animal model. Forty-eight cylindrical implants were inserted into the trabecular bone of the lateral and medial femoral condyles of twelve goats according to a split plot design. After an implantation period of twelve weeks, the bone-implant interface was evaluated histologically. Quantitative histomorphometrical measurements demonstrated a significant difference in bone contact between implants inserted in the lateral and medial condyles. In addition, a significant difference in bone apposition was observed between the coated and the uncoated implants. Finally, all Ca-P coatings showed reduction in coating thickness. Measurements revealed that FA and HAHT showed less reduction in coating thickness than HA coating. Despite the coating reduction, the bone remained in close contact with the implant surface.

Analysis of Variance↗

PubMed1995

Histological evaluation of a biodegradable Polyactive/hydroxyapatite membrane.

Guided tissue regeneration (GTR) is a technique which is used for the treatment of bone defects associated with periodontal disease or enossal dental implants. In most experimental studies on GTR, non-degradable membranes are used. A drawback inherent to such devices is that at the end or in the course of the wound healing they have to be removed. Therefore, the aim of the present study was to investigate a new biodegradable membrane material for use in GTR, which also has excellent mechanical properties and is biocompatible. The material is a composite consisting of poly(ethyleneglycol terephthalate) and poly(butylene terephthalate) segmented copolymer (PEG/PBT), which for the experiments was used in pure form and also mixed with hydroxyapatite (HA) grains. Subcutaneous and subgingival implantation studies in goats were performed to determine the biocompatibility and biodegradability characteristics of several of these materials. Differences between materials were introduced in the production process, PEG/PBT ratio, material thickness and presence of HA. Implantation periods were 3, 6 and 12 wk. The histological results indicated that all investigated materials were biocompatible with the surrounding tissue. Degradation of the membranes was attended by a mild cellular reaction. The degradation process was mainly influenced by the PEG/PBT ratio. A higher PBT content resulted in a decreased degradation.

Animals↗

PubMed1995

A review of the preclinical pharmacology of tiagabine: a potent and selective anticonvulsant GABA uptake inhibitor.

We review the neurochemical and behavioral profile of the selective gamma-aminobutyric acid (GABA) uptake inhibitor, (R)-N-(4,4-di-(3-methylthien-2-yl)but-3-enyl) nipecotic acid hydrochloride [tiagabine (TGB), previously termed NNC 05-0328, NO 05-0328, and NO-328], which is currently in phase III clinical trials for epilepsy. TGB is a potent, and specific GABA uptake inhibitor. TGB lacks significant affinity for other neurotransmitter receptor binding sites and/or uptake sites. In electrophysiological experiments in hippocampal slices in culture, TGB prolonged the inhibitory postsynaptic potentials (IPSP) and inhibitory postsynaptic currents (IPSC) in the CA1 and CA3 produced by the addition of exogenous GABA. In vivo microdialysis shows that TGB also increases extracellular GABA overflow in a dose-dependent manner. Together these biochemical data suggest that the in vitro and in vivo mechanism of action of TGB is to inhibit GABA uptake specifically, resulting in an increase in GABAergic mediated inhibition in the brain. TGB is a potent anticonvulsant agent against methyl-6,7-dimethyoxy-4-ethyl-B-carboline-3-carboxylate (DMCM)-induced clonic convulsions (mice), subcutaneous pentylenetetrazol (PTZ)-induced tonic convulsions (mice and rats), sound-induced convulsions in DBA/2 mice and genetically epilepsy-prone rats (GEPR), and electrically induced convulsions in kindled rats. TGB is partially efficacious, against subcutaneous PTZ-induced clonic convulsions, and photically induced myoclonus in Papio papio. TGB is weakly efficacious in the intravenous PTZ seizure threshold test and the maximal electroshock seizure (MES) test and produces only partial protection against bicuculline (BIC)-induced convulsions in rats. The overall biochemical and anticonvulsant profile of TGB suggests potential utility in the treatment of chronic seizure disorders such as generalized clonic-tonic epilepsy (GTCS), photomyoclonic seizures, myoclonic petit mal epilepsy, and complex partial epilepsy.

Animals↗

PubMed1995

Stress and arousal in deployment of a combat support hospital.

Two hundred thirty-nine soldiers from the 28th Combat Support Hospital were evaluated for stress and arousal during deployment preparations for Operation Uphold Democracy. We measured stress and arousal using the Stress Arousal Checklist and found increased levels of arousal in officers and older soldiers. We also found higher levels of arousal in soldiers reporting a greater number of hours of sleep during the preceding 24 hours. We found no significant difference in stress scores for several demographic and coping behavior groups. Based on lower arousal scores, younger, sleep-deprived, and enlisted soldiers may be at the highest risk for accidents during deployment preparations.

Adaptation, Psychological↗

PubMed1994

Fibroblast response to microtextured silicone surfaces: texture orientation into or out of the surface.

Previous studies suggested that surface topographic configurations of 1-3 microns influence cellular behavior and tissue response. They did not address which specific aspect of the configurations elicits the cellular response. We therefore investigated the effect of the orientation of several surface configurations. Seven different textures on polydimethyl siloxane (silicone; Dow Corning Silastic) specimens were used to test the question of whether orientation into (down) or out of the surface (up) affected cellular response to a material. The textures were smooth and photoetched configurations of 2 microns up, 2 microns down, 5 microns up, 5 microns down, 10 microns up, and 10 microns down. The response of cultured fibroblasts on these surfaces was compared with that of a standard tissue culture material, polyethylene terepthalate (Thermanox). The cell density was measured over a 12-day period with the use of a colorimetric assay. The uptake of methylene blue was measured daily and compared as an absorbance in a destaining agent. Cells on the 2 and 5 microns up arrays showed increased rates of proliferation and cell density as compared with their down counterparts. This would indicate that textures of 2 and 5 microns have a significant influence on cell growth, and that the surface with hills has a greater effect than the surface with wells. In contrast, the 10 microns up and 10 microns down arrays did not prove to be statistically different from smooth ones. This indicates that the orientation effect is related to the configuration size and that this configuration size is not viewed differently from smooth silicone by the cells. The presented data are in agreement with results of this laboratory and others that fibroblasts recognize the dimensions of surface configurations and react accordingly. Specifically, they appear to react to the uppermost surface area presented to them, but conclusive data can only be obtained from a study of the focal adhesions.

Adult↗

PubMed1994

Tissue reaction to soft-tissue anchored percutaneous implants in rabbits.

This study reports on the soft-tissue response to titanium fiber mesh percutaneous implants. The implants were inserted in the backs of 15 rabbits. The surgical procedure was performed in two steps: implantation of the subcutaneous part of the implants and, after 3 months, fixation of the percutaneous part into the subcutaneous part. Two and 6 months after insertion the animals were sacrificed and the implants, with their surrounding tissues, were processed histologically. Light microscopic analysis demonstrated that only one implant showed considerable skin retraction in the percutaneous area. Around the rest of the implants no downgrowth or only a very limited epidermal downgrowth was observed. Furthermore, the fiber mesh material showed good biocompatible behavior. These results confirm the previous finding that sintered titanium fiberweb structures are effective for the stabilization of percutaneous devices located in soft tissues and can improve their performance.

Animals↗

PubMed1994

Titanium fiber mesh anchorage for percutaneous devices applicable for peritoneal dialysis.

In previous experiments a new type of percutaneous device for implantation in soft tissue was designed. The subcutaneous component of the new device consists of a sintered titanium fiber web. The percutaneous devices are inserted by a so-called "two-phase" surgical technique with an intervening healing period of 3 months between the insertion of the subcutaneous flange and the placement of the percutaneous part. From a clinical point of view, this time interval is too long. Therefore, the aim of this study was to investigate a possible reduction of the intervening healing period. The implants were inserted in the backs of 18 rabbits. In each rabbit, six implants were placed with intervals of 1 week. Consequently, at the end of the experiment, in each rabbit six implants were present with implantation periods ranging from 5-10 weeks. After 10 weeks, the animals were sacrificed and the implants with their surrounding tissues were processed histologically. Light microscopic and histomorphometric analysis demonstrated that there was no difference in tissue response between the various implantation periods. Furthermore, it was found that the fiber mesh material showed good biocompatible behavior. In conclusion, the experiment has demonstrated that for titanium mesh percutaneous devices a 5-week healing period is sufficient between the installation of the subcutaneous and percutaneous parts.

Animals↗

PubMed1994

Study of the surface characteristics of magnetron-sputter calcium phosphate coatings.

Plasma-sprayed hydroxylapatite coatings on metals such as titanium have been investigated for many years and have shown a good biocompatibility when implanted in bony tissues. Radiofrequency magnetron sputtering was used as an alternative method to deposit thin films of hydroxylapatite on titanium substrates. X-ray diffraction demonstrated that the sputtered layer was crystalline with a preferred (001) crystallographic orientation with the C-axis perpendicular to the substrate surface. Scanning electron microscopy showed that the deposited films had a uniform and dense structure. The calcium phosphate ratio varied between 1.5 and 2.0, as determined by energy-dispersive X-ray analysis. The in vitro dissolution appeared to be determined by the degree of the coating's crystallinity.

Biocompatible Materials↗

PubMed1994

Histological assessment of sintered metal-fibre-web materials.

Recently it has been shown that flexible metal fibre mesh structures can be used for the subcutaneous stabilisation of percutaneous devices. However, for the safe application of fibre mesh structures, it is necessary that these materials possess certain biological properties. The purpose of this paper is to discuss surgical, statistical and histological methods for the testing and evaluation of metal fibre web materials for soft tissue application. The use and potential of the described techniques are demonstrated with two examples.

Alloys↗

PubMed1993

Histological and histomorphometrical evaluation of the bone reaction to three different titanium alloy and hydroxyapatite coated implants.

The aim of this study was to investigate the bone response to three different types of titanium (Ti) alloys and hydroxyapatite (HA) coated titanium alloy by histological and histomorphometrical analysis. Therefore, implants made of these materials were inserted into the tibia of rabbits. Implantation times were 6 and 16 weeks. The histological evaluation included measurement of the amount of bone apposition and analysis of the bone reaction and interface characteristics around the implants. The results demonstrated no marked differences in bony reaction to the different implant materials. In addition, the HA coatings showed loss of thickness.

Bone Remodeling↗

PubMed1993

A histological and histomorphometrical investigation of fluorapatite, magnesiumwhitlockite, and hydroxylapatite plasma-sprayed coatings in goats.

Plasma-sprayed ceramic coatings of fluorapatite (FA), magnesiumwhitlockite (MW), and hydroxylapatite (HA), and noncoated Ti-6Al-4V alloy (Ti) implants were evaluated histologically and histomorphometrically in a goat animal study. Cylindrical Ti-6Al-4V plugs were plasma-spray-coated with FA, MW, and HA. Noncoated, grit-blasted Ti plugs served as controls. The plugs were implanted into the right femur and left humerus of 20 adult goats. The results were evaluated using descriptive histology and histomorphometry. The histomorphometry consisted of measurements of bone apposition and coating thickness. The results demonstrated that FA showed a high amount of bone apposition without signs of degradation or dissolution. MW showed considerable reduction in thickness and at 12 weeks an adverse tissue reaction. However, at 25 weeks the amount of bone apposition was significantly increased compared with the 12-week implants. HA revealed considerable and progressive reduction in thickness and at 25 weeks a lower amount of bone apposition than FA and MW. At 12 weeks the Ti implants did reveal bone apposition, although frequently localized fibrous tissue was visible. At 25 weeks the Ti implants did not differ in bone apposition from the HA implants. Further studies are necessary on the effect of degradation or dissolution of HA on the compatibility with bone.

Alloys↗

PubMed1993

Histologic investigation of the biologic behavior of different hydroxyapatite plasma-sprayed coatings in rabbits.

The aim of this study was to investigate bone response to and biostability of three different hydroxyapatite (HA)-coatings. Therefore, coated and uncoated titanium implants were inserted into the tibia of rabbits. Implantation times were at 3 and 12 weeks. The histological evaluation included measurement of the amount of bone apposition to the various implant surfaces. The results demonstrated at 3 and 12 weeks no marked differences in bony reaction at the cortical level to the different implant materials. However, compared with the 3-week specimens, at 12 weeks extensive maturation of the woven bone callus had occurred. In addition, all 12-week implants induced bone formation in the medullary cavity. It was also noted that all HA-coatings showed loss of coating thickness. Quantitative determination of bone contact demonstrated that all 12-week implants showed the same high amount of bone apposition.

Animals↗

PubMed1993

Application of magnetron sputtering for producing ceramic coatings on implant materials.

Radiofrequent magnetron sputtering was used to produce calcium phosphate coatings on metal and plastic substrates. Scanning electron microscopy showed that the deposited films had a uniform thickness and a dense columnar structure. Energy-dispersive X-ray analysis, X-ray crystal diffraction and atomic absorption spectrometry demonstrated that the sputtered layer was well-crystallized calcium phosphate ceramic with a Ca/P ratio varying between 1.9 and 2.5. The biocompatibility of the coatings was determined by in vitro and in vivo experiments. It was found that the coatings were biocompatible without any sign of adverse tissue reaction. It was concluded that magnetron sputtering is a promising method for forming a biocompatible ceramic coating onto an implant material. Nevertheless, several problems have to be solved before magnetron sputtering can be used on a routine basis for the production of Ca/P coatings.

Animals↗