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PubMed1987

Orally ingested microencapsulated urease and an adsorbent, zirconium phosphate, to remove urea in kidney failure.

Dialysis is the conventional treatment for chronic renal failure. It is cumbersome, expensive and time-consuming and thus alternate treatments have long been sought. A compact system consisting of haemoperfusion in series with ultrafiltration can nearly replace dialysis. A urea removal system is the only step required to complete this approach. The potential of combining a microencapsulated enzyme, urease, with an ammonium ion adsorbent, zirconium phosphate, to remove urea was examined in vitro. Urease converts urea to ammonium ions which are then adsorbed onto zirconium phosphate. This combination would be most effective in the intestinal tract. The capacity of zirconium phosphate is probably not enough to effect the removal of enough urea to completely replace dialysis in patients with no renal function. However, this system could potentially 1) delay the onset of dialysis therapy in patients who still have some renal function, either alone or in combination with haemoperfusion-ultrafiltration, or 2) reduce dialysis treatment times.

Adsorption↗
PubMed1977

Acute lung lesions due to zirconium and aluminum compounds in hamsters.

The lung lesions produced by multiple short-term intratracheal instillations of saline solutions of sodium zirconium lactate (NaZL), zirconium-aluminum-glycine hydroxychloride complex (ZAG), and aluminum chlorhydrate (ACH) in hamsters were studied by light and electron microscopy. These solutions produced lesions beginning with exudative pneumonia followed by pneumonitis (interstitial pneumonia) and foreign body granulomas. Electron microscopic microprobe analysis demonstrated the metallic component of the instilled compounds in membrane-bound cytoplasmic inclusions of macrophages. The lesions produced by NaZL and ZAG were similar to those produced by ACH. These lesions were also similar to those in previous reports of aerosol exposure of animals to zirconium or aluminum, or to other unrelated compounds.

Aluminum↗
PubMed1981

Evaluation of an occupational respiratory exposure to a zirconium-containing dust.

A group of handfinishers of zirconium metal reactor components questioned whether the dust to which they were exposed would cause chronic lung disease or cancer, or both. To investigate this possibility, the work environment was surveyed, and 32 male employees who had worked as handfinishers from one to seventeen years, were compared to a group of controls in reference to a respiratory questionnaire, chest x-ray findings, and expiratory lung function tests. The controls were matched to the handfinishers for age, sex, payroll status and smoking history. No significant differences were found between the exposed and the control groups. Results of earlier animal respiratory studies vary from no effect to definite pathology. Previous employee exposure studies are short-term and have methodological shortcomings. It would appear that lifetime animal respiratory studies and systematic epidemiological studies of employee populations with long-term inhalation exposure are needed to demonstrate unequivocally whether zirconium and zirconium compounds are harmful.

Cross-Sectional Studies↗
PubMedDate not supplied

Interstitial lung granulomas as a possible consequence of exposure to zirconium dust.

A case of interstitial lung granulomas is described in a worker exposed to zirconium compounds. Chest X-rays revealed diffuse slight reticular interstitial radio-opacities (ILO classification, 1/0 s/t). Histological examination of transbronchial biopsy tissue revealed small interstitial nonconfluent granulomas with epithelioid and giant cells showing no central necrosis, with PAS-positive diastase-resistant small weakly birefringent particles in interstitial histiocytes. These histological and stain findings, which are characteristic of zirconium skin lesions and granulomas, suggest zirconium interstitial lung disease.

Adult↗
PubMed2000

Novel binuclear chiral zirconium catalysts used in enantioselective strecker reactions.

A novel binuclear chiral zirconium catalyst was successfully used in enantioselective Strecker reactions. The catalyst was readily prepared from zirconium t-butoxide (Zr(OtBu)4), (R)-6,6'-dibromo-1, 1'-bi-2-naphthol ((R)-6-Br-BINOL), and (R)-3,3'-dibromo-1, 1'-bi-2-naphthol ((R)-3-Br-BINOL) to form unique binuclear structure. It was revealed that a combination of (R)-6-Br-BINOL and (R)-3-Br-BINOL was essential in these asymmetric reactions and that much lower selectivities were obtained by using other combinations. Two-component (an imine and hydrogen cyanide (HCN)) and three-component (an aldehyde, an amine, and HCN) Strecker reactions proceeded smoothly in the presence of a catalytic amount of the chiral zirconium catalyst to afford the corresponding alpha-amino nitrile derivatives in high yields with high enantioselectivities.

Journal Article↗
PubMed2001

Zirconium alkoxides in catalysis.

This paper presents recent advances in the reactions catalyzed by zirconium alkoxide. Catalytic asymmetric reactions with chiral zirconium catalysts and redox reactions are first discussed. The diverse characteristics of zirconium alkoxides as Lewis acids, Brönsted bases, and nucleophiles, are key for promoting these unique reactions. Our recent development of novel reactions, one-pot synthesis of trans-1.2-diol derivatives and trans-beta-cyanohydrins from olefins, is also described. These reactions cannot be produced using other metals.

Journal Article↗
PubMed2001

Direct determination of boron and zirconium in ceramic materials by flame atomic absorption spectrometry after alkali sintering and fusion.

Both boron and zirconium are present in ceramic materials as major silica components and have to be determined for quality control in the ceramic industry. For boron determination, sintering with a mixture of Na2CO3 and ZnO is proposed for decomposition of samples. For zirconium determination, acid digestion using an HF-HClO4 mixture and subsequent fusion with NaKCO3 and H3BO3 is proposed as decomposition step. The AAS absorbance signal of these elements is suppressed by the fusion elements in the samples. Therefore, the calibration solutions for both B and Zr must contain an appropriate concentration of sodium, sodium-potassium, and boron salts. An AIF3 solution was used for signal enhancement and improving the linearity of the Zr calibration curve. The methods proposed are well suited for the determination of higher concentrations of both boron and zirconium in silicate samples.

Journal Article↗
PubMed2002

Layered zirconium phosphate chloride dimethyl sulfoxide as a two-dimensional exchanger of anionic ligands. Part I. Substitution of chloride with inorganic monodentate ligands.

Crystalline ZrPO(4)Cl(CH(3))(2)SO was prepared by direct precipitation in the presence of oxalic acid as a zirconium complexing agent. The structure of ZrPO(4)Cl(CH(3))(2)SO, refined with the Rietveld method using X-ray powder diffraction data, was confirmed to be close to that of the compound prepared using gamma-zirconium phosphate as a precursor. Chloride anions directly bonded to zirconium were found to act as weak ligands; this made possible their replacement with other monodentate anionic ligands. The preparation and a preliminary characterization of a series of inorganic derivatives obtained by topotactic replacement of Cl with OH, Br, MSO(4) (M = H, NH(4), Na), NaMoO(4), and HCrO(4) anions is reported. The possibility of replacement of chloride also with organic anions, such as alkoxides and carboxylates, and the possibility of substituting also dimethyl sulfoxide with other neutral ligands, as shown by preliminary study, makes ZrPO(4)Cl(CH(3))(2)SO a useful and very flexible precursor for materials chemistry.

Journal Article↗
PubMed2006

Syntheses and X-ray crystal structures of zirconium(IV) and hafnium(IV) complexes containing monovacant wells-Dawson and Keggin polyoxotungstates.

The syntheses and crystal structures of a series of zirconium(IV) and hafnium(IV) complexes with Dawson monovacant phosphotungstate [alpha2-P2W17O61](10-) and in situ-generated Keggin monovacant phosphotungstate [alpha-PW11O39](7-), which was obtained by a reaction of [alpha-PW12O40](3-) with Na2CO3, are described. K15H[Zr(alpha2-P2W17O61)2].25H2O (K-1), K16[Hf(alpha2-P2W17O61)2].19H2O (K-2), (Et2NH2)10[Zr(alpha-PW11O39)2].7H2O (Et2NH2-3), and (Et2NH2)10[Hf(alpha-PW11O39)2].2H2O (Et2NH2-4), being afforded by reactions in aqueous solutions of monolacunary Dawson and Keggin polyoxotungstates with ZrCl2O.8H2O and HfCl2O.8H2O followed by exchanging countercations, were obtained as analytically pure, homogeneous colorless crystals. Single-crystal X-ray structure analyses revealed that the Zr(IV) and Hf(IV) ions are in a square antiprismatic coordination environment with eight oxygen atoms, four of them being provided from each of the two monovacant polyanion ligands. Although the total molecular shapes and the 8-coordinate zirconium and hafnium centers of complexes 1-4 are identical, the bonding modes (bond lengths and bond angles) around the zirconium(IV) and hafnium(IV) centers were dependent on the monovacant structures of the polyanion ligands. Additionally, the characterization of complexes 1-4 was accomplished by elemental analysis, TG/DTA, FTIR, and solution (31P and 183W) NMR spectroscopy.

Journal Article↗
PubMed1997

Structure of the interface between rabbit cortical bone and implants of gold, zirconium and titanium.

The role of surface properties (chemical and structural) for the interaction between biomaterials and tissue is not yet understood. In the present study, implants made of titanium, zirconium (transition metals with surface oxides) and gold (metallic surface) were inserted into the rabbit tibia. Light microscopic (LM) morphometry showed that after 1 and 6 mo the gold implants had less amount of bone within the threads and a lower degree of bone-implant contact than the titanium and zirconium implants, which did not differ from each other. These quantitative differences were supported by LM and ultrastructural observations of the interface. The ultrastructural observations in addition demonstrated that the layer of non-collagenous amorphous material located between the implant and the calcified bone was appreciably thicker around zirconium than around titanium implants. The factors potentially responsible for the observed morphological differences in the bone around the different material surfaces are discussed.

Journal Article↗
PubMed2004

Melting behavior of one-dimensional zirconium nanowire.

In this paper, we analyze the melting behavior of zirconium nanowire using the results of a series of molecular dynamics simulations. Our calculation employs a well-fitted, tight-binding many-body potential for zirconium atoms. The melting point of the nanowire is predicted by the root-mean-square displacements for inner and outer shells. Our simulations predict two melting behaviors: one is the inner melting and the other is the outer melting. Our results reveal that the melting of nanowire starts from the inner shell atoms. The melting point of zirconium nanowire is lower than the bulk value (2125 K). Moreover, the melting point of the inner shell is lower than that of the outer shell. A coexistence of crystal and liquid units is observed in the melting process of nanowire. An investigation of local clusters is carried out to further analyze the melting mechanism of the nanowire. The presence of the local clusters 1331, 1321, 1211, etc. is an indication of disordered structures. The pair and angular correlation functions are also presented for the analysis of the melting behavior. It is not only the diffusion of single atom but the diffusion of clusters result in the occurrence of the melting.

Journal Article↗
PubMed2004

Air-stable, storable, and highly efficient chiral zirconium catalysts for enantioselective Mannich-type, aza Diels-Alder, aldol, and hetero Diels-Alder reactions.

For the synthesis of optically active compounds, chiral catalysts have attracted much attention because large quantities of optically active molecules can be prepared from a small amount of a chiral source. However, many chiral catalysts are often unstable in air (oxygen) and/or in the presence of water. This is especially the case in chiral Lewis acid catalysis, because most Lewis acids are air- and moisture-sensitive. Therefore, many catalysts are prepared in situ in an appropriate solvent just before use, and they cannot be stored for extended periods. We have developed air-stable, storable, and highly efficient chiral zirconium Lewis acids. The catalysts promoted asymmetric Mannich-type, aza Diels-Alder, aldol, and hetero Diels-Alder reactions efficiently with high enantioselectivities. A key to stabilizing the catalysts is an appropriate combination of chiral zirconium Lewis acids with molecular sieves, and the zirconium-molecular sieves-combined catalysts can be stored for extended periods in air at room temperature without loss of activity. Moreover, it has been demonstrated that the catalysts can be recovered and reused.

Journal Article↗
PubMed2005

Interaction of cells with L-lactide/glycolide copolymers synthesized with the use of tin or zirconium compounds.

Comparative studies have been carried out on the viability of cells culture and production of collagen on lactide/glycolide copolymers synthesized using zirconium or tin initiators. Cell response of various cell types: fibroblast-like cells, osteoblast-like cells, monocyte/macrophage-like cells has been examined. Cell response depends on the kind of cells and the initiator used during the synthesis of the polymer. In a number of cases the cells grown on materials containing zirconium have been reported to have better survival (for example, Saos2 cells). An enhanced collagen production on these copolymers has been also observed.

Biocompatible Materials↗
PubMed1978

Ultrastructural observations on epithelioid cell granulomas induced by zirconium in the guinea-pig.

An ultrastructural study has been made of the allergic-type nodular granulomas that can be induced in guinea-pigs sensitised to sodium zirconium lactate. Lesions taken at the peak of granuloma development 7 days after skin testing contained epithelioid cells which could be recognised particularly by their content of rough endoplasmic reticulum, fimbriated cell membrane and typical nuclear appearance. Multinucleate giant cells were also seen. These cells were characterised by their large number of lysosome-like dense bodies and phagocytic structures. Both epithelioid cells and multinucleate giant cells were similar to those described in zirconium granulomas in man. However, these cells differed in a number of respects from similar cells observed in human sarcoidosis. A constant feature of the guinea-pig lesions was the presence of large numbers of apparently active fibroblasts.

Animals↗
PubMed2000

Determination of biokinetic parameters for ingestion of radionuclides of zirconium in animals using stable tracers.

Exposure to the radioactive isotope 95Zr, as in nuclear accidents, and to stable zirconium, due to its use in industry, has increased the interest in the biokinetics of this element. Information has been derived mainly from tests performed on animals by means of radioactive tracers. Due to the fact that extrapolation from animals to humans is always open to question, there is an increasing need of a methodology which allows data to be obtained directly from humans. The use of stable tracers, being ethically justifiable, is a powerful tool for providing this information. As two tracers of the same element must be utilized in order to evaluate gut absorption, an analytical technique which is capable of distinguishing and measuring simultaneously different isotopes of zirconium in biological samples is required. Preliminary tests on laboratory animals were performed in order to assess the feasibility of the double tracer technique combined with proton activation analysis.

Animals↗
PubMed1977

Experimental studies of sensitization to beryllium, zirconium, and aluminum compounds in the rabbit.

In a study designed to assess the potential sensitizing and granulomagenic capacities of selected metallic salts, rabbits were inoculated intradermally with zirconium aluminum glycinate (ZAG), sodium zirconium lactate (NZL), aluminum chlorhydrate (ACH), BeSO 4, and ovalbumin (OVA) by single and multiple injections. Animals immunized with BeSO4 and with OVA developed delayed skin reactivity as well as antigen-specific alveolar macrophage migration inhibition. Neither single nor multiple injections of ZAG or ACH resulted in clear-cut positive skin reactivity, macrophage migration inhibitory factor (MIF) production, or lymphocyte stimulation. Rabbits inoculated with multiple injections of NZL (500 microng) showed some marginally positive macrophage migration inhibition and skin reactivity. Histologically, ZAG and ACH were found to induce well-organized foreign-body granulomas after intradermal injection in both normal and inoculated rabbits. NZL and BeSO4 also induced skin granulomas, but these were less organized and distinct. Cell viability and ultrastructural studies indicated that BeSO4 was highly toxic for isolated alveolar macrophages in vitro at concentrations above 10 microng/ml, but NZL and ZAG did not exert such an effect at these dose levels. BeSO4 also depressed lymphocyte stimulation in sensitized animals which demonstrated delayed skin reactivity and macrophage migration inhibition.

Aluminum↗
PubMed2005

Removal of p-aminophenol and p-nitrophenol from aqueous solution through adsorption on antimony, cadmium, and zirconium ferrocyanides.

Adsorptive interaction of p-aminophenol and p-nitrophenol in the concentration range 10(-4)-10(-5) M and at room temperature (30+/-1 degrees C) was studied with antimony, cadmium, and zirconium ferrocyanides. The interaction followed the Langmuir type of adsorption in general. The p-nitrophenol was found to have greater affinity for the antimony, cadmium, and zirconium ferrocyanides then the p-aminophenol.

Adsorption↗
PubMed2005

In vitro retentive strength of zirconium oxide ceramic crowns using different luting agents.

STATEMENT OF PROBLEM: In contrast to gold crowns, in vitro determination of the retentive strength of all-ceramic crowns is more difficult because components allowing connection to testing apparatus are not as easily integrated into the all-ceramic material. Nevertheless, retentive strength data are crucial for obtaining information about the potential clinical performance of luting cements for all-ceramic restorations. Therefore, a new in vitro model was necessary to evaluate the retentive strength of all-ceramic crowns. PURPOSE: The purpose of this in vitro study was to determine the retentive strength of 4 resin-cement systems, a compomer, a glass-ionomer cement, a resin-modified glass-ionomer cement, and a self-adhesive resin for luting zirconium oxide ceramic crowns. MATERIAL AND METHODS: One-hundred-twenty extracted human teeth were randomly divided into 12 groups (n = 10) and prepared in a standardized manner (5-degree taper, 3-mm occlusogingival height). All-ceramic crowns (Lava) were fabricated in a standardized manner for each tooth. The following cements and corresponding bonding regimens were used to lute the crowns to the teeth according to manufacturers' recommendations: CO, Compolute/EBS Multi; CO/RT, Compolute/EBS Multi/Rocatec; CB, Superbond C and B; CB/RT, Superbond C and B/Rocatec; CB/PL, Superbond C&B/Porcelain Liner M; PA, Panavia F; DC, Dyract Cem Plus/Xeno III; CH/PL, Chemiace II/Porcelain Liner M; RL, RelyX Luting, K/C, Ketac Cem/Ketac Conditioner; K, Ketac Cem; and RU, RelyX Unicem. After thermal cycling (5000 cycles, 5 degrees C-55 degrees C), the outer surfaces of the cemented zirconium oxide ceramic crowns were treated (Rocatec) to improve bonding and then placed into a low-shrinkage epoxy resin block (Paladur). The block/crown and tooth components for each specimen were connected to opposing ends of a universal testing machine so that crown retention could be measured. Crowns were removed from teeth along their path of insertion. The retentive surface area (mm 2 ) was determined individually for each tooth. Statistical analyses were performed using the Wilcoxon exact test, (alpha =.05) and a Bonferroni correction (alpha =.001). RESULTS: The median (minimum/maximum) retentive strength values (MPa) were as follows: CO, 1.7 (0.6/4.3); CO/RT, 3.0 (1.3/5.4); CB, 4.8 (3.7/7.9); CB/RT, 8.1 (4.2/12.7); CB/PL, 5.3 (3.7/10.2); PA, 4.0 (3.3/5.1); DC, 3.3 (2.1/5.6); CH/PL, 4.0 (1.3/6.3); RL, 4.7 (2.8/6.6); K/C, 1.8 (0.6/2.3); K, 1.9 (0.2/4.5); and RU, 4.8 (2.5/6.7). Superbond C&B (+ Rocatec) specimens showed the highest median retentive strength, but were not significantly different from Superbond C&B without Rocatec pretreatment of the all-ceramic crown's inner surface. Compolute specimens also did not benefit significantly from the Rocatec pretreatment. Within the materials used without pretreatment of the ceramic, Superbond C&B, Panavia, Dyract Cem Plus, RelyX Luting, and RelyX Unicem showed the highest median retentive strength values and were not significantly different. CONCLUSION: Within the conditions of this study, the compomer-cement, the resin-modified glass-ionomer cement, and the self-adhesive resin luting agent had the same level of retentive quality as the resin luting agents, Superbond C&B, and Panavia. Rocatec pretreatment of the ceramic surface did not improve the retentive strengths of Compolute and Superbond C&B.

Cementation↗