Comparison of plasma-sprayed hydroxyapatite coatings and zirconia-reinforced hydroxyapatite composite coatings: in vivo study.

The clinical use of plasma-sprayed hydroxyapatite (HA) coatings on metal implants has been widely adopted because the HA coating can achieve the firmly and directly biological fixation with the surrounding bone tissue. However, the long-term mechanical properties of HA coatings has been concern for the long-term clinical application. Previous research showed that the concept of adding ZrO2 as second phase to HA significantly increased the bonding strength of plasma-sprayed composite material. The present work aimed to explore the biological properties, including the histological responses and shear strength, between the plasma-sprayed HA and HA/ZrO2 coating, using the transcortical implant model in the femora of canines. After 6 and 12 weeks of implantation, the HA coating revealed the direct bone-to-coating contact by the backscattered electron images (BEIs) of scanning electron microscope (SEM), but the osseointegration was not observed at the surface of HA/ZrO2 coating. For new bone healing index (NBHI) and apposition index (AI), the values for HA implants were significantly higher than that for HA/ZrO2 coatings throughout all implant periods. After push-out test, the shear strength of HA-coated implants were statistically higher than HA/ZrO2 coated implants at 6- and 12-week implantation, and the failure mode of HA/ZrO2 coating was observed at the coating-bone interface by SEM. The results indicate that the firm fixation between bone and HA/ZrO2 has not been achieved even after 12-week implantation. Consequently, the addition of ZrO2 could improve the mechanical properties of coatings, while the biocompatibility was influenced by the different material characteristics of HA/ZrO2 coating compared to HA coatings.

Expression and distribution of Na, K-ATPase in gill and kidney of the spotted green pufferfish, Tetraodon nigroviridis, in response to salinity challenge.

Freshwater (FW) spotted green pufferfish (Tetraodon nigroviridis) were transferred directly from a local aquarium to fresh water (FW; 0 per thousand ), brackish water (BW; 15 per thousand ), and seawater (SW; 35 per thousand ) conditions in the laboratory and reared for at least two weeks. No mortality was found. To investigate the efficient mechanisms of osmoregulation in the euryhaline teleost, distribution and expression of Na,K-ATPase (NKA) in gill and kidney of the pufferfish were examined and the osmolality, [Na+] and [Cl-] of the blood were assayed. The lowest levels of both relative protein abundance and activity were found to be exhibited in the BW group, and higher levels in the SW group than FW group. In all salinities, branchial NKA immunoreactivity was found in epithelial cells of the interlamellar region of the filament and not on the lamellae. Relative abundance of kidney NKA alpha-subunit, as well as the NKA activity, was found to be higher in the FW pufferfish than fish in BW or SW. Renal NKA appeared in the epithelial cells of distal tubules, proximal tubules, and collecting tubules, but not in glomeruli, in fish groups of various salinities. Plasma osmolality and chloride levels were significantly lower in FW pufferfish than those in BW and SW, whereas plasma sodium did not differ among the groups. Although identical distributions of NKA were found in either gill or kidney of FW-, BW- or SW-acclimated spotted green pufferfish, differential NKA expression in fish of various salinity groups was associated with physiological homeostasis (stable blood osmolality), and illustrated the impressive osmoregulatory ability of this freshwater and estuarine species in response to salinity challenge.

The cell attachment and morphology of neonatal rat calvarial osteoblasts on the surface of Ti-6Al-4V and plasma-sprayed HA coating: effect of surface roughness and serum contents.

The biocompatibility of material plays an important role in the bone-implant interface for the prosthetic implant fixation. The biocompatibility of implants is associated with the chemical composition, surface topography, surface energy and surface roughness of biomaterials. The effects of two factors, surface roughness and serum contents, on osteoblast behavior at the surface of Ti-6Al-4V and plasma sprayed HA coating were investigated in the experiment. The osteoblasts derived from neonatal rat calvarial were cultured in Dulbecco's modified Eagle medium (DMEM) with fetal bovine serum (FBS) on the surface of polished Ti-6Al-4V (Ti-p), grit-blasted Ti-6Al-4V (Ti-b), polished HA coating (HAC-p), and as-sprayed HA coating (HAC). Under culture medium containing 4% FBS, the level of cell attachment to the polished surface is significantly higher than the rough surface of the same experimental materials during all culture periods. Increasing the contents of FBS up to 10%, the difference of osteoblast attachment is not found between Ti-p and Ti-b. Under 4% serum condition, the cell morphology attached to smooth surfaces (Ti-p and HAC-p) is spread faster and are more flattened than the one to rough surface of the same experimental materials by SEM. After 24 h culture, the corroded cracks are easily observed at the surface of polished HA coatings, and the cell morphology on HAC-p coatings are elongated and less flattened compared with Ti-p. The result is consistent with statistical difference of cell attachment between Ti-p and HAC-p under 4% serum condition.

Biological responses of neonatal rat calvarial osteoblasts on plasma-sprayed HA/ZrO2 composite coating.

Plasma-sprayed hydroxyapatite (HA) coating, applied to metal substrates, can induce a direct chemical bond with bone and hence achieve a biological fixation of the implant. However, the poor bonding strength between the HA coating and the substrate has been a concern for the orthopedists. In a previous study, the zirconia-reinforced hydroxyapatite composite coatings (HA/ZrO(2)) could significantly improve the mechanical strength before and after soaking in simulated body fluid. This study aims to investigate the biological responses of osteoblasts on plasma-sprayed HA/ZrO(2) coating. The osteoblasts derived from neonatal rat calvarial were cultured in Dulbecco's modified Eagle medium (DMEM) with fetal bovine serum (FBS) on the surface of plasma-sprayed HA coating, HA/ZrO(2) coating, and ZrO(2) coating, respectively. The biological responses were investigated by the cell growth (1, 3, 5, and 10 days) and the cell morphology under scanning electron microscopy (SEM) (3, 6, 12, 24 and 48 h). Examination by SEM revealed that osteoblasts on HA coatings exhibit less spreading during the medium phase (6 and 12 h), while, better morphologies were observed at the latter phases (24 and 48 h). This should be derived by the dissolution of HA coating in the culture medium. On HA/ZrO(2) coating, the cells showed the poor morphologies at the latter phases (24 and 48 h). This could be explained by the no apatite formed at the surface HA/ZrO(2) coating after soaking in simulated body fluid. The lower contents of ZrO(2) coating in HA coating and the addition of other solid solution (ZrO(2)-MgO, CaO-ZrO(2), ZrO(2)-CeO(2)) in HA coating are the two possible methods to improve the cytocompatibility of HA/ZrO(2) coating.

Isolation, identification, and synthesis of sex pheromone components of female tea cluster caterpillar,Andraca bipunctata walker (Lepidoptera: Bombycidae) in Taiwan.

Octadecanal (18:Ald), (E)-11-octadecenal (E11-18:Ald), (E)-14-octadecenal (E14-18:Ald) and (E,E)-11,14-octadecadienal (E11,E14-18:Ald) were isolated and identified as major components from the pheromone glands of the tea cluster caterpillar,Andraca bipunctata, in Taiwan by analyzing the mass spectra of gland components and their DMDS adducts. GC retention times and mass spectra of the components were in agreement with those of authentic synthetic compounds. The average amount of 18:Ald,E11-18:Ald,E14-18:Ald andE11,E14-18:Ald per female gland (1 to 3 days old) was 121±76, 50±20, 187±75, and 237±110 ng, respectively, in a ratio of 20:8:31:41. SyntheticE11,E14-18:Ald caught more males than each of the other three components or blank control in field trapping tests.E11,E14-18:Ald is reported as an insect sex pheromone for the first time. Male antenna responded toE11,E14-18:Ald strongly in an EAG analysis. Furthermore, 4 hr after the injection of PBAN (pheromone biosynthetic activating neuropeptide) into decapitated female moths (2 days old), the percentage of theE11,E14-C18 Ald in the gland extract increased from 0% to 75.5%, which was also significantly more than that of unligated and uninjected control at 55.1%. All these data indicated thatE11,E14-18:Ald is the sex pheromone of theAndraca bipunctata in Taiwan.

Structure-affinity relationships of baclofen and 3-heteroaromatic analogues.

Substituting a furan, a thiophene, a benzo[b]furan, a benzo[b]thiophene, or a quinoline ring for the p-chlorophenyl moiety of baclofen has led to GABAB ligands with different affinities depending on the nature of the heteroaromatic ring, and on the nature and position of its substituent. As steric effects cannot account for all the affinity variations, we have studied the lipophilic and electronic properties of baclofen and selected 3-heteroaromatic analogues, gaining insight into the structural features necessary for GABAB affinity. Centrifugal partition chromatography (CPC) has been used to measure octan-1-ol water distribution coefficients, while ab initio molecular orbital (MO) calculations were performed to study electronic properties.

Mechanism of ligand binding to alpha 1-acid glycoprotein (orosomucoid): correlated thermodynamic factors and molecular parameters of polarity.

Eight ligands were used in this study, four basic, three neutral and one acidic. Their binding to serum alpha 1-acid glycoprotein (orosomucoid) was measured at several temperatures, and the data were analysed together by a general model with three unknowns, number of binding sites, delta H0 and delta S0. The partition coefficients of the ligands were measured in octanol/water and heptane/water systems (log Poct. and log Phep.), and their molecular volumes were calculated by molecular modelling techniques. These structural properties allow determination of polarity parameters (delta log Poct.-hep., lambda oct. and lambda hep.) which encode in different proportions the various polar interactions between the solute and the aqueous and organic phases, i.e. hydrogen-bonding capacity and dipolarity/polarizability. This study shows that good correlations exist between delta H0 or delta S0 and polarity parameters, such that the enthalpic contribution to binding increases with increasing polarity of the ligands, mainly hydrogen-bond-donor acidity, whereas their entropic contribution to binding decreases.

Structure-genotoxicity relationships of allylbenzenes and propenylbenzenes: a quantum chemical study.

Quantum mechanical calculations at the semiempirical level (AM1 method) were conducted for estragole (1), methyleugenol (2), safrole (3), alpha-asarone (4), beta-asarone (5), elemicin (6), allylbenzene (7), eugenol (8), trans-anethole (9), isosafrole (10), and myristicin (11), and the results compared with the known genotoxicity of 1-6 and the absence of genotoxicity of 7-11 (unscheduled DNA synthesis assay). The various compounds showed no significant differences in the relative stability of the radical species formed as intermediates in C-sp3 hydroxylation (delta HR(radical)) and in the corresponding enthalpy of activation (delta H++). In contrast, the carbonium ions of the genotoxic congeners 1-6 were shown to be comparatively more stable than those of the inactive compounds 7-11, with the exception of eugenol (8). The inactivity of this compound could be due to a very rapid stabilization of the carbonium ion by deprotonation to form a quinone methide, as suggested by quantum chemical calculations. The relative stability of the carbonium ion thus appears to be one of the key factors in the genotoxicity of allylbenzenes and propenylbenzenes.

Clinical pharmacology of oxicams: new insights into the mechanisms of their dose-dependent toxicity.

Six oxicams, sudoxicam, isoxicam, piroxicam, tenoxicam, meloxicam and lornoxicam, were compared in an attempt to understand why, despite close chemical structures, two of them were associated with an increased risk of toxicity in patients. Different factors have been revealed which may explain these differences. A weak association constant to human serum albumin (HSA), together with a high plasma concentration, favours a rapid increase in unbound concentration (Cu) when total plasma concentration rises (peak of absorption). Pathological states may enhance this increase when both HSA plasma concentration is decreased and free fatty acid concentrations are increased. However, the main cause of toxicity may be the existence in some subjects of HSA natural mutants whose ability to bind oxicams is markedly lower than normal.

Effects of solvation on the ionization and conformation of raclopride and other antidopaminergic 6-methoxysalicylamides: insight into the pharmacophore.

Previous work has shown that raclopride in water at neutral pH exists in a zwitterionic form, suggesting a stereoelectronic structure largely different from that of other benzamides. In the present study, the acid-base behavior of other 6-methoxysalicylamides is shown to be comparable to that of raclopride. An extensive investigation by high-temperature molecular dynamics gave insight into the conformational behavior of neutral and zwitterionic raclopride in vacuum and in water. Partitioning of raclopride and a more rigid analogue with characterization (by first-derivative UV spectroscopy) of the predominant forms in the organic phase indicated that only neutral, internally H-bonded forms partition into the organic solvent. Thus, the predominant forms of 6-methoxysalicylamides will be very different in the aqueous and organic phases. In the latter phase, and hence presumably also in the receptor phase, the drugs exist with a neutral, internally H-bonded phenolic group and are therefore stereoelectronically similar to other substituted benzamides.

Percutaneous penetration of drugs: a quantitative structure-permeability relationship study.

Human skin permeation data taken from the literature were analyzed for quantitative relationships with physicochemical properties and structural descriptors. No correlations exist with molecular weights and solvent-accessible surface areas. In most cases, skin permeation was inversely correlated with the parameter delta log Poct-hep (i.e., log Poctanol minus log Pheptane), which is mainly a measure of the H-bond donor acidity of the solutes. Lipophilicity itself, as expressed by log Poctanol, also contributes positively to skin permeation in some cases. The results of this quantitative structure-permeability relationship study are interpreted in terms of a unified mechanistic model whereby drugs can permeate via an intercellular route (correlation with both delta log Poct-hep and log Poct) and/or a transcellular route (correlation with log Poct only).

Affinity partitioning of vancomycin.

The use of the Flanagan and Barondes model(14) describing affinity partitioning as an aid in designing separation systems is discussed. Experimental studies are described for affinity partitioning of vancomycin, a glycopeptide antibiotic, in a water-methoxypolyethylene glycol-dextran system using methoxypolyethylene glycol-dextran system using methoxypolyethylene glycol bound D-alanyl-Dalanyl-D-alanine or D-alanyl-D-alanine as the reversible affinity ligand. Even for this ideal case of 1:1 binding interaction, the model only qualitatively predicts the affinity effect when all model parameters are measured independently. The discrepancy between measured and predicted values can be attributed to a difference in exposed surface of the free antibiotic and ligand compared to that in the bound state.The effect of experimentally varying model parameters is also described. It was determined that a polymers-ligand which partitions more strongly to the top phase would provide the most significant enhancement to this affinity partitioning system. Such an improvement can be made by increasing the molecular weight of the hydrophobicity of the polymer-ligand. A process for vancomycin recovery from fermentation broth using D--alanyl-D-alanine sepharose as affinity ligand is described.

Partitioning of solutes in different solvent systems: the contribution of hydrogen-bonding capacity and polarity.

Published partition coefficient values of 121 solutes in five solvent systems (1-octanol-water, n-heptane-water, chloroform-water, diethyl ether-water, and n-butyl acetate-water) were correlated with solute properties, namely intrinsic molecular volume (indicator of cavity formation) and the solvatochromic parameters pi* (dipolarity/polarizability), beta (H-bond acceptor basicity), and alpha (H-bond donor acidity). While the cavity term and the H-bond accepting capacity played a comparable role in all solvent systems, the H-bond donor acidity was significant only in the alkane-water and chloroform-water systems. Comparison of the regression coefficients of pi*, beta, and alpha demonstrated the important role that water content at saturation in the organic solvents plays in the partitioning of solutes. Analysis of the differences between 1-octanol-water and n-heptane-water partition coefficients (delta log Poct-hep) and between 1-octanol-water and chloroform-water partition coefficients (delta log Poct-chf) showed that these values mainly quantitate the capacity of solute to donate hydrogen bonds. In contrast, the differences between 1-octanol-water and diethyl ether-water or n-butylacetate-water partition coefficients, (delta log Poct-dee and delta log Poct-ba, respectively) contain no structural information.

Determination of lipophilicity and hydrogen-bond donor acidity of bioactive sulphonyl-containing compounds by reversed-phase HPLC and centrifugal partition chromatography and their application to structure-activity relations.

The lipophilic character of two large series of substituted benzenesulphonamides (BzSA) and 4-aminodiphenylsulphones (4-ADS) has been assessed by two chromatographic methods, i.e. reversed-phase HPLC using a relatively novel octadecylpolyvinyl packing and centrifugal counter-current chromatography (CPC). The octadecylpolyvinyl stationary phase proved an interesting alternative to the more common octadecylsilane type stationary phase for obtaining retention parameters correlated to partition coefficients (i.e. log P). The CPC method, being far less time-consuming and markedly more precise than the classical shake-flask method, offers a promising alternative for measuring partition coefficients. The parameter delta log Poct-hep, i.e. log Poctanol minus log Pheptane, was also determined for both congeneric series and was indicative of a similar H-bonding capacity for the SO2NH2 and 4-NH2-C6H4-SO2 groups. QSAR analyses of carbonic anhydrase inhibition by BzSA and antimycobacterial activity of 4-ADS show the capacity of the new lipophilicity parameters to express the hydrophobic component of the drug-enzyme interactions and to reveal a possible role of H-bond donor capacity in governing the antimycobacterial activity of 4-ADS.