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At least 163 records · Page 9Linked to original sources
PubMed1987

Absence of promotion potential for calcium L-ascorbate, L-ascorbic dipalmitate, L-ascorbic stearate and erythorbic acid on rat urinary bladder carcinogenesis.

The effects of treatment with calcium L-ascorbate, L-ascorbic dipalmitate, L-ascorbic stearate and erythorbic acid on two-stage urinary bladder carcinogenesis in F344 rats after initiation with N-butyl-N-(4-hydroxybutyl)nitrosamine (BBN) were examined. Carcinogen was administered at a dose of 0.05% in drinking water for 4 weeks and thereafter the test chemicals were given as a 5% supplement in the diet for the following 32 weeks. No increase in the induction of preneoplastic lesions, papillomas or carcinomas was apparent and it was concluded that none of the test chemicals possess promoting activity for urinary bladder carcinogenesis.

Animals↗
PubMed1989

The products of the reduction of doxyl stearates in cells are hydroxylamines as shown by oxidation by 15N-perdeuterated Tempone.

The use of nitroxides in functional biological systems has increased greatly as it has become evident that such studies can provide valuable biophysical and metabolic data. This has led to a need to understand the nature of the metabolism of nitroxides and their products. This paper presents data indicating the value of 15N-perdeuterated Tempone specifically to indicate the amount of hydroxylamines that are present in a cellular system. Using this technique, we found that in the mammalian cells that we studied the principal or only products of reduction of doxyl stearates were the corresponding hydroxylamines.

Animals↗
PubMed1996

Improved electrochemical properties of stearate-graphite paste electrodes after albumin and phospholipid treatments.

Stearate-graphite paste electrodes (SGEs) exhibit enhanced dopamine sensitivity and insensivity to asorbic acid electrocatalytic effects in vitro following exposure to unidentified contituents of rat brain tissue homogenates. The present study utilized voltammetry and chronamperometry to compare the electrochemical characteristics of brain-treated SGEs to those treated with potential brain constituent candidates (albumin proteins and phospholipids). Albumin treatments markedly attenuated interference from ascorbate catalytic effects whereas lipids enhanced both electrode capacitance and sensitivity to dopamine. Combined treatments resulted in electrochemical properties that were similar to brain-treated SGEs. Potential mechanisms by which albumin may attenuate ascorbate electrocatalysis of dopamine were investigated using high performance liquid chromatography, with electrochemical detection. The reduction in ascorbate electrocatalytic effects at albumin-treated SGEs may be due to nucleophilic binding of dopamine oxidation products to albumin attached to the electrode surface. Therefore, the unambiguous detection of dopamine by SGEs in vivo may be related to interactions with factors in brain having similar surface-modifying properties.

Animals↗
PubMed2006

Infrared study on annealing effect on conformation of zinc stearate.

The molecular conformation and thermal transition behavior of two zinc stearate specimens, unannealed one and annealed one, were compared. The unannealed specimen has one thermal transition at 134 degrees C. Annealing was made by increasing temperature to 150 degrees C and cooling to room temperature slowly. This annealed specimen has an exothermic peak at 103 degrees C, and endothermic shoulders and a peak at 118, 124 and 131 degrees C, respectively. The observed frequencies of all bands of the unannealed specimen at room temperature are assigned to the all-trans conformation. We found new bands at 858, 823, 793, 766, 688, and 604 cm-1 for the annealed specimen. Based on the normal mode analyses, these bands are assigned to the TGT conformation at the COO end, where T means trans and G means gauche. The annealed specimen consists of almost all-trans molecule but partial molecules have the TGT conformation.

Calorimetry, Differential Scanning↗
PubMed1972

Direct determination of the structure of barium stearate multilayers by x-ray diffraction.

Diffraction of X-rays is recorded from barium stearate multilayer systems with from 2 to 60 double layers or unit cells. The generalized Patterson function P'(x) is calculated by an integral Fourier transform of observed intensity data from a specimen containing only two unit cells. The Patterson function P(0)(x) of a single unit cell is determined from P'(x) and the electron density distribution of a bimolecular leaflet is obtained by a deconvolution procedure of P(0)(x) after Hosemann and Bagchi. The electron density distribution is also calculated independently by a conventional Fourier synthesis with an experimentally established set of phases. The results of the two methods are consistent and fit a physical model of the bimolecular leaflet. A direct analysis, therefore, can be performed if diffraction is observed from multilayer systems with a small number of unit cells.

Barium↗
PubMed2001

Micelles self-assembled from poly(ethylene oxide)-block-poly(N-hexyl stearate L-aspartamide) by a solvent evaporation method: effect on the solubilization and haemolytic activity of amphotericin B.

The goal of this study was to assess a solvent evaporation method for the encapsulation of amphotericin B (AmB) in poly(ethylene oxide)-block-poly(N-hexyl stearate L-aspartamide) (PEO-b-PHSA) micelles. By the solvent evaporation method, PEO-b-PHSA self-assembled into small spherical micelles with a high AmB content based on transmission electron microscopy, size exclusion chromatography and absorption spectroscopy. The encapsulation of AmB was slightly better than an earlier method based on dialysis. Importantly, AmB in PEO-b-PHSA micelles encapsulated by the solvent evaporation method was non-haemolytic at 15 microg/ml, whereas AmB in PEO-b-PHSA micelles encapsulated by the dialysis method caused 50% haemolysis at the level of 3.8 microg/ml, and AmB itself caused 100% haemolysis at 1.0 microg/ml. Thus, PEO-b-PHSA micelles could effectively encapsulate AmB, increase the overall water solubility of AmB and reduce the toxicity of the membrane-acting drug, particularly by a solvent evaporation method.

Amphotericin B↗
PubMed2000

Developmental toxicity of 2-ethylhexyl stearate.

2-Ethylhexyl stearate was investigated in an embryo-/foetotoxicity and teratogenicity study on rats according to OECD guidelines for the testing of chemicals (No. 414). Dose levels of 0 (arachidis oil), 100, 300 and 1000mg/kg body weight/day were administered by gavage. Dams tolerated the applied dose levels without any toxic effects. Pre- and post-implantation loss and mean numbers of resorptions were unaffected by treatment. All parameters were comparable with the animals of the control group. Skeletal and visceral investigations revealed no treatment-related malformations. For embryo-/foetotoxicity, teratogenicity and maternal toxicity a NOAEL of 1000mg/kg was deduced.

Abnormalities, Drug-Induced↗
PubMed2001

On the difficulty of assessing the specific surface area of magnesium stearate.

The water content of as-received commercial magnesium stearate batches from animal and vegetable sources have been modified by ageing in humid air at room temperature or by vacuum treatment. The complete adsorption-desorption isotherms of nitrogen and krypton vapours by samples of these as received and modified materials have been measured at liquid nitrogen temperature after standardised vacuum degassing. They are greatly affected by the initial water content of the material. In particular: (a) the BET surface area values computed from the adsorption branch vary widely and is increasing with increasing water content; (b) anomalous hysteresis of varying amplitude is observed in all cases except adsorption of krypton on the material with the lowest water content; (c) the hysteresis loops extend down to very low desorption pressure values and cannot be accounted for by capillary condensation. Lastly, the surface area value of a given material computed from nitrogen and krypton adsorption may differ by a factor as high as six. Accordingly, the very significance of BET surface area values obtained from routine adsorption experiments should be regarded as questionable, at least until the mechanisms of adsorption are fully clarified.

Adsorption↗
PubMed2005

Acid soap and phase behavior of stearic acid and triethanolamine stearate.

Crystals of partially neutralized stearic acid with triethanolamine (TEA) were prepared by mixing these two materials above 80 degrees C and then cooling. The crystalline composition and the structure and melting behavior of the resultant products were characterized with small-angle and wide-angle X-ray diffraction, thermal analysis, microscopy, and infrared spectroscopy. It was discovered that an acid-soap complex of 2:1 fixed stoichiometric ratio exists between stearic acid and TEA stearate. A binary phase diagram of stearic acid and TEA soap is built based on the experimental results; this is the first published record of a binary phase diagram for amine-based soap. Its behavior is significantly different from that of binary systems of fatty acid and alkali soap.

Acids↗
PubMed2006

Contrasting melting behavior of zinc stearate and zinc oleate.

The influence of a double bond in the middle of an otherwise flexible hydrocarbon chain on the melting of such assemblies has been investigated by comparing the melting behavior of zinc stearate and zinc oleate. By monitoring features in the infrared spectra that are characteristic of the global conformation of the hydrocarbon chain, it is shown that the double bond effectively decouples the thermal evolution of conformational disorder in the chain segments on either side of the double bond and the melting of each of these segments in the assembly occurs as independent events.

Calorimetry, Differential Scanning↗
PubMed1997

Mechanistic evaluation of binary effects of magnesium stearate and talc as dissolution retardants at 85% drug loading in an experimental extended-release formulation.

The feasibility of producing extended-release matrix tablets with high drug loadings (80-90% w/w) containing a binary combination of magnesium stearate (MS) and talc (T) at different levels as major dissolution retardants was investigated. Matrix tablets were prepared from a granulation containing theophylline, starch, hydroxypropylcellulose, and varying amounts of MS and T. Using a 32 factorial design, the effect of MS and T levels on the physical properties and drug release characteristics of the tablets was evaluated. Response surface analysis showed that the binary combination of MS and T at levels >3% adversely affected both tensile strength and friability. A parabolic relationship was observed for the increase in time required for the release of 50% of the theophylline (t50%) with increased MS levels. Moreover, as the proportion of MS and T was increased, the release profiles became more linear. A combination of 3% MS and T provided both near zero-order release kinetics as well as a coherent matrix structure. Based on model fitting, a release mechanism combining diffusion and matrix erosion/dissolution is proposed. It may be concluded that in the development of controlled-release systems, the binary combination of MS and T at levels exceeding those conventionally used for lubrication can be employed as an inexpensive, low bulk dissolution retardant for formulations with high drug loading.

Chemical Phenomena↗
PubMed2006

Phase transitions and microstructure of emulsion systems prepared with acylglycerols/zinc stearate emulsifier.

The emulsification processes, during which acylglycerols/zinc stearate emulsifier, water, and oil phase formed ternary systems, such as water-in-oil (W/O) emulsions, oil-in-water (O/W) dispersions, and unstable oil-water mixtures, were investigated in order to characterize the progressive transformations of the dispersed systems. The type, structure, and phase transitions of the systems were found to be determined by temperature and water phase content. Crystallization of the emulsifier caused the destabilization and subsequent phase inversion of the emulsions studied, at a temperature of 60-61 degrees C. The observed destabilization was temporary and led, at lower temperature, to W/O emulsions, "O/W + O" systems, or O/W dispersions, depending on the water content. Simultaneous emulsification and cooling of 20-50 wt % water systems resulted in the formation of stable W/O emulsions that contained a number of large water droplets with dispersed oil globules inside them ("W/O + O/W/O"). In water-rich systems (60-80 wt % of water), crystallization of the emulsifier was found to influence the formation of crystalline vesicle structures that coexisted, in the external water phase, with globules of crystallized oil phase. Results of calorimetric, rheological, and light scattering experiments, for the O/W dispersions obtained, indicate the possible transition of a monostearoylglycerol-based alpha-crystalline gel phase to a coagel state, in these multicomponent systems.

Journal Article↗
PubMed2001

Antiproliferative and apoptotic effect of ascorbyl stearate in human glioblastoma multiforme cells: modulation of insulin-like growth factor-I receptor (IGF-IR) expression.

Human glioblastomas (gliomas) are characterized as highly invasive and rapidly growing brain tumors. In this study, we present data on in vitro effect of ascorbyl stearate (Asc-S), a liphophilic derivative of ascorbic acid on cell proliferation, transformation, apoptosis and modulation of expression of insulin-like growth factor-I receptor (IGF-IR) in human glioblastoma multiforme (T98G) cells. Asc-S showed significant inhibition of fetal bovine serum and human recombinant insulin-like growth factor-I (IGF-I) dependent cell proliferation in a dose dependent manner. Treatment of T98G cells with 0, 50, 100 and 150 microM Asc-S for 24h slowed down the cell multiplication cycle with significant accumulation of cells at late S/G2-M phase of cycle. Asc-S treatment (100 microM) reversed the transformed phenotype as determined by clonogenecity in soft agar and also induced apoptosis of T98G. These changes were found to be associated with significant decrease in IGF-IR expression in dose and time dependent manner compared to untreated controls. The data clearly demonstrate that Asc-S has antiproliferative and apoptotic effect on T98G cells probably through modulation of IGF-IR expression and consequent facilitation of programmed cell death.

Agar↗
PubMed2003

Antiproliferative and proapoptotic effect of ascorbyl stearate in human pancreatic cancer cells: association with decreased expression of insulin-like growth factor 1 receptor.

Pancreatic cancer is an aggressive tumor with short median survival and high mortality rate. Alternative therapeutic modalities are currently being evaluated for pancreatic cancer. Here we studied the effects of ascorbyl stearate (Asc-S), a nontoxic, lipophilic derivative of ascorbic acid, on pancreatic cancer. Treatment of human pancreatic carcinoma cells with Asc-S (50-200 microM) resulted in a dose-dependent inhibition of their proliferation. Asc-S slowed down the cell cycle, accumulating, PANC-1 cells in late G2-M phase. Furthermore, Asc-S treatment (150 microM) markedly inhibited growth in soft agar and facilitated apoptosis of PANC-1 cells but not of Capan-2 cells. These effects were accompanied by a significant reduction in insulin-like growth factor 1 receptor (IGF1-R) expression, as compared to untreated controls. Interestingly, Capan-2 cells, the least responsive to Asc-S treatment, did not overexpress the IGF1-R. The results demonstrate the efficacy of Asc-S in inhibing growth of pancreatic cancer cells and warrant additional studies to explore the potential utility of this compound as an alternative and/or adjuvant therapeutic modality for pancreatic cancer.

Apoptosis↗
PubMed2006

Enhancing the bioavailability of cyclosporine a using solid dispersion containing polyoxyethylene (40) stearate.

Solid dispersion containing polyoxyethylene (40) stearate and cyclosporine A was prepared by solvent-melt method and characterized using differential scanning calorimetry, powder X-ray diffraction, and Infrared Fourier Transform Spectroscopy (FTIR). Dissolution of the drug from solid dispersion was dramatically enhanced compared to that from the drug powder alone and physical mixture. In vivo oral bioavailability of cyclosporine A from the solid dispersion in Wistar rats was comparable to that from a commercial product, Sandimmun Neoral (P>0.05). The formulation is stable up to six months under 30 degrees C/RH60% and one year at 25 degrees C/RH 60% when packed in aluminum-polyethylene laminated bags.

Animals↗
PubMed1984

Studies on the effects of ingestion of a single 500 mg oral dose of erythromycin stearate on leucocyte motility and transformation and on release in vitro of prostaglandin E2 by stimulated leucocytes.

Polymorphonuclear leucocyte (PMNL) and mononuclear leucocyte (MNL) migration to the leucoattractant endotoxin-activated serum as well as MNL mitogen-induced transformation were measured in normal adult volunteers before and 1 1/2 h and 96 h after the ingestion of a single oral dose of 500 mg of erythromycin stearate. Ingestion of the antibiotic was associated with a significant increase in PMNL migration at 1 1/2 h with a return to normal levels at 96 h. Slight but insignificant enhancement of MNL migration and of transformation to mitogens was detected after erythromycin. The mechanism of the slight stimulation of MNL transformation, which was consistently observed, was investigated further in vitro by measuring the effects of erythromycin base on the release of prostaglandin (PG) E2 by mitogen-stimulated MNL. Similar studies were performed using leuco-attractant-exposed PMNL. Inhibition of PGE2 release was observed for both MNL and PMNL with therapeutic concentrations of erythromycin. To assess the possible in-vivo significance of the immunopotentiating properties of the antibiotic the effect of a single intraperitoneal injection of 250, 500 or 1000 micrograms on the survival time of mice lethally infected with the erythromycin-resistant microorganism Candida albicans were investigated. Pre-treatment of the mice with erythromycin at each concentration used significantly increased the mean survival times. It is possible that these non-specific immunostimulatory properties of erythromycin potentiate in-vivo antimicrobial activity.

Adjuvants, Immunologic↗
PubMed1986

An in-vitro study of oral therapeutic doses of co-trimoxazole and erythromycin stearate on abnormal polymorphonuclear leucocyte migration.

The effects of administration for four days of co-trimoxazole (2 X 500 mg tablets daily) and erythromycin stearate (3 X 500 mg tablets daily) on persistently abnormal polymorphonuclear leucocyte (PMNL) migration in six individuals with a history of chronic or recurrent bacterial infections were studied. The effects of co-incubation of PMNL in vitro with both antimicrobial agents at concentrations of 12(-5) and 10(-4) M were also investigated. Two different leucoattractants were used, autologous serum activated with bacterial endotoxin (EAS) and the synthetic chemotactic tripeptide FMLP. In three homosexual males with the acquired immunodeficiency syndrome (AIDS) abnormal PMNL motility was associated with the presence of serum inhibitor(s) of cell migration. In a fourth female subject, with recurrent episodes of acute periodontitis, and intrinsic cellular defect of PMNL migration associated with markedly impaired FMLP-induced degranulation and binding to PMNL was observed. In the remaining two subjects with chronic osteomyelitis, the precise abnormality of PMNL movement was not defined but appeared to be of the cellular intrinsic type. Co-incubation of PMNL with erythromycin, but not cotrimoxazole, at both concentrations tested (10(-5) and 10(-4) M) significantly improved cell migration to EAS, Likewise administration of erythromycin, but not cotrimoxazole, significantly improved PMNL migration to EAS. Improvement or correction of abnormal PMNL motility during antimicrobial chemotherapy with erythromycin may be a useful property of this antimicrobial agent.

Acquired Immunodeficiency Syndrome↗
PubMed1988

Efficacy and tolerability of erythromycin acistrate and erythromycin stearate in acute skin infections of patients with atopic eczema.

The efficacy and tolerability of a new erythromycin derivative, erythromycin acistrate (EA), were compared with that of erythromycin stearate (ES) in 42 patients with infected atopic eczema. The dosage of EA was 400 mg tid and that of ES 500 mg tid. The duration of treatment ranged from five to 12 days. The patients were hospitalized and evaluated before treatment and on the last day in hospital. The infective pathogen was usually Staphylococcus aureus in both groups. Without local antibacterial treatment both drugs eradicated the bacteria in more than 60% of the cases. Gastrointestinal side effects were frequently reported with both drugs, more often in the ES- than in the EA-group, but the difference was only statistically significant (p less than 0.05) with respect to diarrhoea. One patient in each group discontinued treatment because of gastrointestinal side effects. No elevations in liver enzymes of clinical significance were reported in either group.

Administration, Cutaneous↗