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At least 1,027 records · Page 57Linked to original sources
PubMed1990

In vitro release of azidothymidine (AZT) by ceramic drug delivery systems.

Conventional methods of administration of 3-azido-2,3-dideoxythymidine (AZT) to treat AIDS patients is associated with negative side effects, including toxic effects on bone marrow. This study was designed to investigate the capability of tricalcium phosphate (TCP) and alumino-calcium-phosphorous oxide (ALCAP) drug delivery systems to release AZT in a sustained manner in an in vitro environment. A total of 35 TCP and 35 ALCAP ceramic capsules were used in this experiment. The final densities of the ceramics were 1.68 +/- 0.11 and 1.58 +/- 0.08 g/cm3 for ALCAP and TCP, respectively. Tricalcium phosphate ceramics were distributed into four groups. Each ceramic in groups I, II and III (n = 10) was loaded with 20, 40, or 60 mg of AZT in powder form, respectively. Group IV ceramics (n = 5) were left empty and served as a control group for possible corrections of absorbance readings. A similar protocol was followed for ALCAP ceramic capsules unless otherwise indicated. All TCP and ALCAP ceramic capsules were sealed at both ends with Silastic Medical Adhesive Silicon Type A (Dow Corning, Midland, MI). Each empty capsule and those loaded with AZT were sealed and suspended in a capped and sealed individual serum bottles containing 100 mls of phosphate buffered saline (pH 7.4), and agitated at 100 cycles per min in a water bath at 37 degrees C. The amount of AZT released from the ceramic reservoir into the buffered medium was measured spectrophotometrically (265 nm). Release of AZT from the ceramic capsule was monitored until the contents of the capsules were depleted.(ABSTRACT TRUNCATED AT 250 WORDS)

Aluminum Oxide↗
PubMed1996

Osmium ammine-B and electron spectroscopic imaging of ribonucleoproteins: correlation of stain and phosphorus.

Ultra-thin sections of Chironomus salivary glands were stained in a non-Feulgen procedure with osmium ammine-B and imaged at several electron energy-loss windows. For two types of RNP-containing structures (ie Balbiani ring granules and endoplasmic reticulum), a significant spatial correlation was observed between stain distribution and net phosphorus distribution. Non-Feulgen osmium ammine-B staining does not require the use of ultra-thin sections and can approximate the distribution of nucleic acid phosphorus.

Animals↗
PubMed1995

Organic molecules in the gas phase of dense interstellar clouds.

Since a previous COSPAR review on this subject, the number of molecular species identified by astronomers in dense interstellar clouds or in the envelopes expelled by evolved stars has grown from about eighty to approximately one hundred. Recent detections in stellar envelopes include the radical CP, the second phosphorus-containing astronomical molecule; SiN, the first astronomical molecule with a Si-N bond; and the HCCN radical. In the dense interstellar clouds recent detections or verifications of previous possible identifications include the H3O+ ion, which is a critical intermediary in the production of H2O and O2; the CCO radical, which is isoelectronic with HCCN; the SO+ ion, which appears to be diagnostic of shock chemistry; two new isomers of cyanoacetylene, HCCNC and CCCNH; and the two cumulenes H2C3 and H2C4. Some recent work is also described on the mapping of interstellar clouds in multiple molecular transitions in order to separate variations in chemical abundance from gradients in physical parameters.

Astronomical Phenomena↗
PubMed2004

The behavior of novel hydrophilic composite bone cements in simulated body fluids.

Composite bone cements were formulated with bioactive glass (MgO--SiO(2)--3CaO. P(2)O(5)) as the filler and hydrophilic matrix. The matrix was composed of a starch/cellulose acetate blend (SCA) as the solid component and a mixture of methylmethacrylate/acrylic acid (MMA/AA) as the liquid component. The curing parameters, mechanical properties, and bioactive behavior of these composite cements were determined. The addition of up to 30 wt % of glass improved both compressive modulus and yield strength and kept the maximum curing temperature at the same value presented by a typical acrylic-based commercial formulation. The lack of a strongly bonded interface (because no coupling agent was used) had important effects on the swelling and mechanical properties of the novel bone cements. However, bone cements containing AA did not show a bioactive behavior, because of the deleterious effect of this monomer on the calcium phosphate precipitation on the polymeric surfaces. Formulations without AA were prepared with MMA or 2-hydroxyethyl methacrylate (HEMA) as the liquid component. Only these formulations could form an apatite-like layer on their surface. These systems, therefore, are very promising: They are bioactive, hydrophilic, partially degradable, and present interesting mechanical properties. This combination of properties could facilitate the release of bioactive agents from the cement, allow bone ingrowth in the cement, and induce a press-fitting effect, improving the interfaces with both the prosthesis and the bone.

Acrylates↗
PubMed2005

Formation of hydroxyapatite onto glasses of the CaO-MgO-SiO2 system with B2O3, Na2O, CaF2 and P2O5 additives.

New bioactive glasses with compositions based on the CaO-MgO-SiO(2) system and additives of B(2)O(3), P(2)O(5), Na(2)O, and CaF(2) were prepared. The in vitro mineralization behaviour was tested by immersion of powders or bulk glasses in simulated body fluid (SBF). Monitoring of ionic concentrations in SBF and scanning electron microscopy (SEM) observations at the surface of the glasses were conducted over immersion time. Raman and infrared (IR) spectroscopy shed light on the structural evolution occurring at the surface of the glasses that leads to formation of hydroxyapatite.

Biocompatible Materials↗
PubMed2005

[Line scanning analysis of white porcelain from Gong Kiln in early Tang dynasty by energy disperse X-ray fluorescence].

Gong kiln, for its long porcelain-firing history, was one of three representative white porcelain kilns in northern China. In order to improve the quality and whiteness of white porcelain, a decorating layer or cosmetic earth was laid on the body surface in Gong kiln during early Tang dynasty, which was able to blot out rough surface and weaken the influence of fuscous body upon surface color. In this paper the main chemical composition of the white porcelain's profile was analyzed by using energy disperse X-Ray fluorescence. The result showed that different materials were used as cosmetic earth during early Tang dynasty, in accordance with the phenomenon under optical microscope. In addition, the glaze belongs to calcium glaze in which plant ash was added.

Calcium Compounds↗
PubMed1985

31P-NMR studies of the oral pathogen Streptococcus mutans: observation of lipoteichoic acid.

We have used 31P-nuclear magnetic resonance spectroscopy to identify phosphorus-containing compounds in whole cells of two serotype c strains of the oral pathogen Streptococcus mutans. The major resonance, centered at 0 ppm in whole cells, was attributed to lipoteichoic acid on the basis of its chemical shift, insensitivity to pH changes, cellular localization and a comparison with spectra obtained with purified lipoteichoic acid from S. mutans. The linewidths of resonances observed for intact cells and purified lipoteichoic acid were moderately narrowed by increasing the ionic strength, and substantially broadened in the presence of the lectin concanavalin A. Experiments with purified lipoteichoic acid suggest that this compound in whole cells is complexed with divalent cations such as Mg2+. Intracellular pools of other phosphorus-containing metabolites were found to be low when compared to the lipoteichoic acid concentration in both starved and glycolyzing cells.

Cell Membrane↗
PubMed1993

The effects of hypothermia on the intracellular pH of erythrocytes studied using 31P NMR and endogenous compounds.

The effects of hypothermia on the intracellular pH of human erythrocytes were studied non-invasively using 31P NMR spectroscopy and the endogenous phosphorus-containing compounds glycerate 2,3-bisphosphate and inorganic phosphate. Specifically, the pH dependence of the 31P NMR chemical shifts of these compounds was used to measure the intracellular pH at 25 and 37 degrees C. The possibility of a non-pH-dependent change on the chemical shifts of the 2-P and 3-P resonances of glycerate 2,3-bisphosphate due to the presence of paramagnetic deoxy-haemoglobin (i.e., a pseudo-contact interaction) was investigated and found to have negligible effect under the present experimental conditions. The most probable reasons for this are that the deoxy-haemoglobin concentration was too small and/or the glycerate 2,3-bisphosphate does not get sufficiently close to the paramagnetic centre to be affected. The change in intracellular pH with temperature was consistent with that predicted by the alphastat hypothesis.

2,3-Diphosphoglycerate↗
PubMed1988

Ceramic systems for long-term delivery of chemicals and biologicals.

Evaluation of devices, drugs, and drug delivery systems have been investigated by both in vitro and in vivo procedures. Ceramic drug delivery systems can be used to evaluate chemicals and biologicals by both in vitro and in vivo procedures. The system can also reduce handling of the animals and facilitate long-term evaluations before conducting clinical trials. To date, ceramic systems have been used to deliver aldosterone, androstanedione, beta-lactoglobulin, bovine serum albumin, chymotrypsin, danazol, difluoromeythylornithine, dihydrotestosterone, estradiol, gamma globulin, gonadotrophic releasing hormone, gossypol, growth hormone, insulin, methylene blue, pepsin, progesterone, and testosterone. The data obtained suggest that ceramic delivery systems can be used in the near future to treat diseases requiring long-term chronic drug therapy as well as disorders caused by deficiency of certain hormones.

Adrenalectomy↗