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Results for “Calcium Compounds”

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At least 271 records · Page 15Linked to original sources
PubMed2005

Functional morphology of the mantle of Nautilus pompilius (Mollusca, Cephalopoda).

This study presents histological and cytological findings on the structural differentiation of the mantle of Nautilus pompilius in order to characterize the cells that are responsible for shell formation. The lateral and front mantle edges split distally into three folds: an outer, middle, and inner fold. Within the upper part of the mantle the mantle edge is divided into two folds only; the inner fold disappears where the hood is attached to the mantle. At the base of the outer fold of the lateral and front mantle edge an endo-epithelial gland, the mantle edge gland, is localized. The gland cells are distinguished by a distinct rough endoplasmic reticulum and by numerous secretory vesicles. Furthermore, they show a strong accumulation of calcium compounds, indicating that the formation of the shell takes place in this region of the mantle. Numerous synaptic contacts between the gland cells and the axons of the nerve fibers reveal that the secretion in the area of the mantle edge gland is under nervous control. The whole mantle tissue is covered with a columnar epithelium having a microvillar border. The analyses of the outer epithelium show ultrastructural characteristics of a transport active epithelium, indicating that this region of the mantle is involved in the sclerotization of the shell. Ultrastructural findings concerning the epithelium between the outer and middle fold suggest that the periostracum is formed in this area of the mantle, as it is in other conchiferan molluscs.

Animals↗
PubMed1977

Influenza virus infection of hamsters. A model for evaluating antiviral drugs.

Inoculation of hamsters with influenza virus [A/PR/8/34 HON 1] produces an inapparent infection which can be monitored by virus titrations of nasal washes or of homogenates prepared from trachea or lung. Antibody can be detected in the serum within 7 days following virus inoculation. Hamsters previously infected were found to be resistant to challenge with the same virus. The utility of this model for evaluating anti-influenza drugs was demonstrated with two compounds. Calcium elenolate, a virucidal agent, reduced the virus titers of nasal washes when the drug was given as nose drops near the time of virus inoculation so as to affect high drug concentrations in the nasal passages. Virazole, an inhibitor of virus replication, reduced the virus titers of the nasal washes when multiple drug treatments were given as nose drops in an effort to provide drug during the time of virus replication. The model described may provide a useful means of evaluating potential antiviral during candidates inasmuch as the drug can be delivered directly into the nasal passages in a non-fatal influenza infection in a convenient laboratory animal.

Administration, Intranasal↗
PubMed1990

Changes in some nutrients of fenugreek (Trigonella Foenum graecum L.) seeds during water boiling.

Fenugreek seeds were boiled in water for various lengths of time (5, 10 and 15 min). Changes in weight, volume, moisture content, total sugars, nitrogen compounds, minerals, phosphorus compounds, phytic acid, amino acids and the in vitro digestibility of the seeds as well as the total solids of the boiling water were determined. Data indicated that there was an increase in both weight and volume as well as the in vitro digestibility of fenugreek seeds especially after the first 5 minutes of boiling. On the other hand, a decrease in the content of total sugars, protein compounds, calcium, magnesium, phytic acid, phosphorus and amino acids was observed. The reduction was accompanied by a gradual increase in the total solids of boiling water.

Amino Acids↗
PubMed1966

Genesis of white rings of the cornea.

White rings of the cornea occur as an occupational injury among limestone workers, especially those who tend kilns converting limestone to calcium oxide. Clinical proof is offered that the ring results from a calcium hydroxide burn involving a very small area of the cornea.

Burns, Chemical↗
PubMed1992

Chemoprevention clinical trials.

As part of a program to develop drugs which will delay or prevent cancer in humans, the Chemoprevention Branch, National Cancer Institute, National Institutes of Health, is sponsoring 12 Phase I and 22 Phase II and III clinical trials. Three agent classes are significantly advanced in the trials. These are the retinoids, including 13-cis-retinoic acid, retinol, and 4-hydroxyphenylretinamide (nine studies), beta-carotene (seven studies), and calcium compounds (three studies). In addition, six promising new compounds are in Phase I or Phase II trials. These are: piroxicam, ibuprofen, oltipraz (a dithiolthione), difluoromethylornithine, glycyrrhetinic acid, and N-acetylcysteine. Key concepts related to the development of cancer chemopreventive agents are (1) the need for long-term administration, (2) the need for oral route of administration, (3) the matching of toxic side effects to degree of cancer risk.

Anticarcinogenic Agents↗
PubMed1981

Capping of monkey pulps with Dycal and a Ca-eugenol cement.

Capping of 120 teeth in four monkeys was performed with Dycal or with a calcium-eugenol cement. The observation periods were 8 days or 90 days. The monkeys were killed, and the teeth were examined histologically. After 8 days, the pulp-tissue reactions were basically the same in the two groups. The tissue adjacent to the exposure site was characterized by varying amounts of necrotic tissue, inflammatory cells, and extravasated erythrocytes. Capping material and dentin chips were displaced into the pulp tissue. Particles from the capping materials were found in vessels, macrophages, and foreign body cells. After 90 days, more hard-tissue formation occurred in the Dycal group than in the Ca-eugenol cement group. The hard tissue was formed by either fibroblasts or the original odontoblasts.

Animals↗
PubMed1992

Toxic effects of omega chrome red ME and its treatment by adsorption.

Toxic effects of Omega Chrome Red ME, a popular textile dye, on the nitrogen fixing cyanobacterium Nostoc calcicola were studied. The growth of N. calcicola was found to be suppressed at 10 and 20 mg liter-1 initial concentrations of dye, whereas a low initial concentration of 5 mg liter-1 slightly favors growth. Removal of the dye was carried out by adsorption using some cheap and unconventional adsorbents like coal, fly ash, wollastonite, and china clay. It has been observed that, in all cases, the low adsorbate concentration, the low temperature, and an acidic medium favor the dye removal process. The process of uptake follows first-order adsorption rate expression and obeys Langmuir's model of adsorption. The removal process is also partially diffusion controlled. Thermodynamic and pH studies were run to explain the results.

Adsorption↗
PubMed1994

Phosphorus removal from piggery effluents of varying quality using lime and physico-chemical treatment methods.

The choice of management practices for the treatment of piggery effluent prior to its disposal to waterways or land is governed by the desire to simultaneously minimise the cost of treatment whilst minimising pollution of the environment. Laboratory experiments were conducted to compare the removal of total and total filterable phosphorus (P) (<0.45 microm) from ortho-phosphate solutions or piggery effluent by hydrated lime or lime kiln dust alone, or from recycled piggery effluent by lime and physico-chemical treatment methods. In addition, the ability of lime to remove P from recycled piggery effluent at an intensive piggery was assessed. Most P in lime treated effluent was present in the >0.45 microm fraction because of the presence of unsettled flocs of P impregnated lime. The efficiency of total P removal by hydrated lime and lime kiln dust decreased as effluent quality declined. The efficiency of removal of total filterable P by hydrated lime or lime kiln dust was not affected by effluent quality. Hydrated lime was more efficient in removing P from effluent or ortho-phosphate solutions, but lime kiln dust was more cost effective. More than 95% of total P was removed from recycled piggery effluent when physico-chemical treatment followed settling with or without lime. The physico-chemical treatment decreased total P mainly by decreasing the number of suspended particles in the effluent and by precipitating some total filterable P as iron, aluminium or calcium compounds.

Journal Article↗
PubMedDate not supplied

Dry mechanochemical synthesis of hydroxyapatites from DCPD and CaO: influence of instrumental parameters on the reaction kinetics.

Mechanochemistry is a possible route to synthesize calcium deficient hydroxyapatite (CDHA) with an expected molar calcium-to-phosphate (Ca/P) ratio +/-0.01. To optimize the experimental conditions of CDHA preparation from dicalcium phosphate dihydrate (DCPD) and calcium oxide by dry mechanosynthesis reaction, we performed the kinetic study varying some experimental parameters. This kinetic study was carried out with two different planetary ball mills (Retsch or Fritsch Instuments). Results obtained with the two mills led to the same conclusions although the values of the rate constants of DCPD disappearance and times for complete reaction were very different. Certainly, the origin of these differences was from the mills used, thus we investigated the influence of instrumental parameters such as the mass and the surface area of the balls or the rotation velocity on the mechanochemical reaction kinetics of DCPD with CaO. Results show that the DCPD reaction rate constant and the inverse of the time for complete disappearance of CaO both vary linearly with (i) the square of the rotation velocity, (ii) the square of eccentricity of the vial on the rotating disc and (iii) the product of the mass by the surface area of the balls. These observations comply with theoretical models developed for mechanical alloying. The consideration of these four parameters allows the transposition of experimental conditions from one mill to another or the comparison between results obtained with different planetary ball mills. These instrumental parameters have to be well described in papers concerning mechanochemistry or when grinding is an important stage in a process.

Biocompatible Materials↗
PubMed2004

Calcium phosphate sol-gel-derived thin films on porous-surfaced implants for enhanced osteoconductivity. Part I: Synthesis and characterization.

Thin sol-gel-formed calcium phosphate (Ca-P) films were formed on sintered porous-surfaced implants as an approach to increasing the rate of bone ingrowth. The films were prepared using either an inorganic precursor solution (with calcium nitrate tetrahydrate and ammonium dihydrogen phosphate) or an organic precursor solution (with calcium nitrate tetrahydrate and triethyl phosphite). We report on the formation and characteristics of the films so formed. Film characteristics were assessed by thin film X-ray diffraction, diffuse-reflectance infrared Fourier transform spectroscopy, X-ray photoelectron spectroscopy, and scanning electron microscopy. In addition, thin sections were prepared either across or parallel to the Ca-P/Ti6Al4V interface and examined by transmission electron microscopy. Both approaches resulted in the formation of nanocrystalline carbonated hydroxyapatite films but with different Ca/P ratios and structures, the Inorganic Route-formed film having a lower Ca/P ratio (1.46 cf 2.10 for the Organic Route-formed film) and having a more irregular topography. An interfacial reaction product (CaTi(2)O(5)) was identified by selected area electron diffraction with the Inorganic Route-formed film only.

Absorptiometry, Photon↗
PubMed2005

The influence of the phosphorus content on the bioactivity of sol-gel glass ceramics.

The aim of this work was to study the influence of the phosphorus on the crystallization and bioactivity of glass-ceramics obtained from sol-gel glasses. For this purpose two sol-gel glasses with a similar composition but one of them containing P2O5 (70% SiO2; 30% CaO and 70% SiO2; 26% CaO; 4% P2O5, mol%) were prepared. Pieces of these glasses were treated at temperatures ranging between 700 degrees C and 1400 degrees C for 3 h. The obtained materials were characterized by XRD, FTIR, SEM-EDS and the biaxial flexural strength was determined in samples heated at 1100 degrees C. In addition, an in vitro bioactivity study in simulated body fluid (SBF) was carried out. The results showed that phosphorus plays an important role in the crystallization of the glasses: it induced the crystallization of calcium phosphate phases, the stabilization of the wollastonite phase at high temperature as well as the crystallization of SiO2 phases at low temperatures. Moreover, the presence of phosphorus produced a heterogeneous distribution of defects in the pieces and, therefore, the flexural strength of samples containing this element decreased. Finally, glass-ceramics obtained from glasses containing phosphorus showed the fastest formation rate of the apatite layer when soaked in SBF.

Body Fluids↗
PubMed2005

Nucleation of biomimetic apatite in synthetic body fluids: dense and porous scaffold development.

The effectiveness of synthetic body fluids (SBF) as biomimetic sources to synthesize carbonated hydroxyapatite (CHA) powder similar to the biological inorganic phase, in terms of composition and microstructure, was investigated. CHA apatite powders were prepared following two widely experimented routes: (1) calcium nitrate tetrahydrate and diammonium hydrogen phosphate and (2) calcium hydroxide and ortophosphoric acid, but using SBF as synthesis medium instead of pure water. The characteristics of the as-prepared powders were compared, also with the features of apatite powders synthesized via pure water-based classical methods. The powder thermal resistance and behaviour during densification were studied together with the mechanical properties of the dense samples. The sponge impregnation process was used to prepare porous samples having morphological and mechanical characteristics suitable for bone substitution. Using this novel synthesis was it possible to prepare nanosized (approximately equal to 20 nm), pure, carbonate apatite powder containing Mg, Na, K ions, with morphological and compositional features mimicking natural apatite and with improved thermal properties. After sintering at 1250 degrees C the carbonate-free apatite porous samples showed a surprising, high compressive strength together with a biomimetic morphology.

Apatites↗
PubMed2005

Preparation and characteristics of a calcium magnesium silicate (bredigite) bioactive ceramic.

In this study, new bredigite (Ca7MgSi4O16) ceramics were prepared by sintering sol-gel-derived bredigite powder compacts at 1350 degrees C for 8 h. The bending strength, fracture toughness and Young's modulus were about 156 MPa, 1.57 MPa m(1/2) and 43 GPa, respectively. The in vitro bioactivity of the bredigite ceramics was evaluated by investigating the apatite-formation ability in simulated body fluid (SBF) and the effect of ionic products from bredigite dissolution on the mouse fibroblasts cell line L929. In addition, the in vitro biocompatibility of the bredigite ceramics was evaluated by osteoblasts adhesion and proliferation assay. The results showed that bredigite ceramics could induce HAp formation in SBF. The products from bredigite dissolution significantly promoted cell growth at a certain concentration range. Furthermore, osteoblasts adhered and spread well on bredigite ceramics, and osteoblasts proliferation on bredigite ceramics was obvious.

Animals↗