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PubMed2000

Infrared and XAFS study on structure and transition behavior of zinc stearate.

Structure and transition behavior of zinc(II) stearate crystal were investigated by infrared and XAFS spectroscopies. Structure of zinc stearate at room temperature was estimated as follows. From XAFS analysis, the coordination number of the carboxylate groups around the zinc atom was evaluated as 4 and the Zn-O distance as 1.95 A. Based on the infrared spectrum and a normal mode analysis, the conformation of the alkyl chain was confirmed as all-trans and the sub-cell packing was considered as parallel type, and also the coordination form of the carboxylate groups was determined as bridging bidentate type. As increasing temperature, zinc stearate has a solid liquid phase transition at 130 degrees C. At the transition, the alkyl chains goes into liquid like state as reported by Mesubi but the coordination structure was confirmed to be maintained.

Molecular Conformation↗
PubMed1967

Rates of entry and oxidation of acetate, glucose, D(-)-beta-hydroxybutyrate, palmitate, oleate and stearate, and rates of production and oxidation of propionate and butyrate in fed and starved sheep.

1. Rates of entry and oxidation of a range of metabolites have been measured in tracheostomized sheep (diet, 800g. of lucerne chaff and 100g. of maize/day) by combining isotope-dilution techniques with the continuous measurement of total respiratory gas exchange, and (14)CO(2) production during the intravenous or intraruminal infusion of (14)C-labelled substrates. 2. Mean entry rates in fed and starved (24hr.) sheep respectively, expressed as mg./min./kg. body wt.(0.75), were: glucose, 5.0 (range 4.8-5.1, 2 observations) and 3.8 (3.2-4.2, 4); acetate, 10.8 (9.1-13.5, 4) and 5.8 (1); d(-)-beta-hydroxybutyrate, 1.4 (1) and 1.5 (0.8-2.4, 4); palmitate, oleate and stearate (starved sheep only) 1.0 (0.6-1.9, 7), 0.9 (0.2-1.6, 10) and 0.9 (0.5-1.1, 11) respectively. 3. Production rates of propionate and butyrate in continuously feeding sheep were 6.4 (4.7-8.3, 4) and 4.3 (3.4-6.1, 4) mg./min./kg.(0.75) respectively, and in starved (24hr.) sheep were 2.5 (2.2-2.9, 2) and 1.0 (0.8-1.2, 2) mg./min./kg.(0.75) respectively. 4. Calculated terminal values for the specific radioactivity of respiratory (14)CO(2) during measurements of entry rates and production rates were used to calculate the contributions of individual substrates to overall oxidative metabolism. Mean values for fed and starved sheep respectively were: glucose, 9.1 (8.6-9.6, 2) and 11.2 (5.9-15.1, 4)%; acetate, 31.6 (26.8-38.1, 4) and 22.1 (1)%; d(-)-beta-hydroxybutyrate, 10.4 (1) and 4.8 (1.9-7.7, 4)%; propionate, 23.0 (13.8-29.9, 4) and 7.1 (6.8-7.4, 2)%; butyrate, 16.5 (13.7-20.5, 4) and 5.3 (5.2-5.3, 2)%; palmitate, oleate and stearate (starved sheep only), 4.7 (2.0-7.7, 7), 4.0 (1.2-6.6, 10) and 4.4 (3.8-5.8, 9)% respectively. The sum of these values for individual substrates in fed and starved sheep, excluding that of beta-hydroxybutyrate and after correction of the glucose value for the known interrelations of this substrate with propionate, accounted for 76% and 58% respectively of total production of carbon dioxide. 5. Calculations based on the proportion of substrate entry directly oxidized indicated that the substrates studied accounted for 63% (fed sheep) and 43% (starved sheep) of total energy expenditure measured by oxygen uptake. The contribution of beta-hydroxybutyrate was excluded, and corrections were made for glucose-propionate interrelations, and for the different rates of oxidation of the methyl and carboxyl fragments of acetate. 6. The present results have been combined with those obtained earlier in this Laboratory to examine the relationships between rates of substrate entry and oxidation, and concentrations of substrate in blood. Rates of entry of acetate, glucose, d(-)-beta-hydroxybutyrate, palmitate and oleate (but not stearate) were well correlated with concentration in blood, and substrate contribution to production of carbon dioxide showed a similar correlation to blood concentration, except with glucose. 7. It was concluded that the general technique is of potential value in providing valid quantitative parameters of animal metabolism.

Acetates↗
PubMed1979

The influence of food on the bioavailability of new formulations of erythromycin stearate and base.

1. The effect of food on the bioavailability of two new formulations of erythromycin, 1) erythromycin stearate, 500 mg (Erythrocin, 250 mg capsule-shaped tablets) and 2) erythromycin base, 500 mg (Eryc, 250 mg capsules containing enteric-coated pellets) was studied in 16 healthy subjects. 2. The study was a balanced, randomized Latin square design and was conducted on 4 days. The four treatments were erythromycin stearate immediately before (EB) and after EA) breakfast and erythromycin base immediately before (eB) and after (eA) breakfast. 3. The mean +/- s.d. maximal plasma erythromycin concentrations were 2.09 +/- 1.06, 0.37 +/- 0.40, 1.8+ +/- 1.15 and 1.91 +/- 1.57 micrograms/ml and the mean +/- s.d. times at which these occurred were 1.3 +/- 0.7, 2.3 +/- 0.9, 4.4 +/- 1.9 and 4.3 +/- 1.1 h for EB, EA, eB and eA respectively. 4. The mean +/- s.d. areas under the curves (0 to 8 h) were 4.99 +/- 2.41, 1.04 +/- 1.57, 4.93 +/- 2.98 and 4.98 +/- 3.14 for EB, EA, eB and eA respectively. 5. The bioavailability of erythromycin stearate was significantly reduced by the prior administration of food, whereas the absorption of the base was not inhibited by food.

Adult↗
PubMed1986

Investigation of the film formation of magnesium stearate by applying a flow-through dissolution technique.

The film formation of magnesium stearate on the surface of acetylsalicylic acid was investigated by applying a flow-through dissolution technique. The effect of mixing time, lubricant surface area, and the addition of colloidal silica was studied. The film formation increased by increasing mixing time. The final level reached was independent of the specific surface area of the lubricants, but granular magnesium stearate gave a lower surface coverage than the powdered lubricants. The lubricating effect was independent of the mixing time and specific surface area of the lubricants. Colloidal silica was found to interact primarily with the free fraction of magnesium stearate.

Aspirin↗
PubMed1990

Enhanced interleukin production after long-term administration of erythromycin stearate.

The effects of erythromycin stearate (10 mg/kg/day) were studied on productions of interleukin (IL)-1 and -2 in mice after a long-term treatment. A 28-day treatment resulted in higher levels of IL-1 production by macrophages and of IL-2 production by splenocytes, while a 7-day treatment did not increase them. T-cell growth factor activity of IL-2 preparation prepared on day 28 of treatment as determined by HT-2 cell proliferation was reduced by about 40% in the presence of anti-murine IL-4 monoclonal antibodies, while control IL-2 activity was not reduced. Furthermore, a 28-day treatment with erythromycin stearate increased concanavalin A-induced blastogenesis of splenocytes significantly. These results suggest that long-term treatment with erythromycin stearate can stimulate host defense by increasing interleukin production.

Animals↗
PubMed1983

Tolerance and efficacy of erythromycin stearate tablets versus enteric-coated erythromycin base capsules in the treatment of patients with acne vulgaris.

In a randomized, and for the investigator, blind study side-effects and efficacy of two oral erythromycin preparations have been compared. Twenty patients with acne vulgaris, predominantly of the face, received erythromycin stearate tablets and another twenty patients received erythromycin enteric-coated base capsules. All patients were given 500 mg twice a day for 2 weeks. An improvement was seen in both groups, most pronounced in patients treated with the stearate tablets. Twenty per cent of the patients given the base preparation withdrew from therapy due to gastro-intestinal side-effects, as compared to 10% in the erythromycin stearate group.

Acne Vulgaris↗
PubMed2006

Influence of aluminum tristearate and sucrose stearate as the dispersing agents on physical properties and release characteristics of eudragit RS microspheres.

The purpose of this research was to investigate the effects of different concentrations of polymer and sucrose stearate, aluminum tristearate as dispersing agents on microsphere properties and performance. The yield values of microspheres were over the 78%, and the encapsulation efficiencies were found to be approximately 73%. Particle sizes of microspheres prepared with aluminum tristearate were between 76 and 448 microm, while that of the microspheres containing sucrose stearate were between 521 and 2000 microm. Morphological and physicochemical properties of microspheres were investigated by scanning electron micrography and differential scanning calorimetry (DSC). DSC analysis indicated that verapamil hydrochloride formed a solid solution with acrylic polymers. In vitro release studies were performed using the flow-through cell method. While approximately 80% of drug was released from the microspheres containing aluminum tristearate in 480 minutes, the same amount of drug was released from microspheres containing sucrose stearate in only 60 minutes. Chemical structures and concentrations of the dispersing agents were clearly effective on the physical properties of microspheres and their drug-release characteristics.

Acrylic Resins↗
PubMed1989

Effect of erythromycin acistrate and erythromycin stearate on human colonic microflora.

The effects of erythromycin acistrate (2'-acetyl erythromycin stearate), a new erythromycin derivative, and erythromycin stearate on the faecal microflora were compared in a randomized cross-over study. 12 healthy volunteers were given either drug 500 mg t.i.d. for 1 week. Their faeces were studied before, immediately after, and 1 week after the drug administration period. After a wash-out period of 4 weeks, the drugs were interchanged. Both erythromycin acistrate and erythromycin stearate induced changes in the normal colonic microflora to about the same extent. The most marked effect was the suppression of gram-negative anaerobic and aerobic rods. Clostridium difficile appeared in 1 subject on both drugs. Also the counts of aerobic gram-positive cocci were altered; enterococci increased in number. An increased resistance to erythromycin was noted among staphylococci and enterococci after both drugs.

Adolescent↗
PubMed2000

[Effect of magnesium stearate on internal failure of Avicel PH 101 tablets].

The effect of the incorporation of different concentrations of magnesium stearate (0, 0.4, 0.8, and 1.2%) on the texture of the tablets from Avicel PH 101 was investigated by means of the examination of their tensile strength and the values of Weibull's modules. It has been found that with an increasing forming pressure the decrease in the tensile strength of tablets is increased. No significant difference in the decrease in tensile strength was found between stearate concentrations of 0.4 and 0.8%. The incorporation of magnesium stearate into the tableting material, by decreasing the friction between the particles, minimizes possible incidence of more marked disorders in the texture of tablets.

Cellulose↗
PubMed1980

Magnesium stearate given perorally to rats. A short term study.

Magnesium stearate was fed to groups of 20 male and 20 female rats at levels of 0, 5, 10 and 20% in a semisynthetic diet for 3 months. Decreased weight gain was found in males in the 20% group. Urolithiasis was found in 8 males and in 7 females in the same group. Reduced relative liver weight was seen in males in the 10% and in the 20% groups, and an increased amount of iron was found in the livers of the 20% group. Nephrocalcinosis was reduced in females in the 20% group. In this experiment the no-effect-level is estimated to be 5% magnesium stearate in the diet, corresponding to 2500 mg/kg body wt/day.

Animals↗
PubMed2002

Parenteral emulsions stabilized with a mixture of phospholipids and PEG-660-12-hydroxy-stearate: evaluation of accelerated and long-term stability.

Different emulsion formulations were prepared using phospholipids (Lipoid S57) and PEG-660-12-hydroxy-stearate (Solutol HS15) as single emulsifiers or in mixtures. The accelerated stability after autoclaving, freezing and centrifugation was investigated. The long-term stability was also studied at different temperatures (4, 20, and 37 degrees C) for 8 months. Emulsion stabilized with phospholipids displayed a stable behavior after the autoclaving and centrifugation, but it broke down after the freezing process. In mixture with Solutol HS15, however, the emulsion showed appropriate shelf stability at different temperatures for 8 months. A change in the particle size of the emulsion prepared only with Solutol HS15 was observed after centrifugation (slight) and after autoclaving (marked). In contrast to phospholipid emulsion, this emulsion (with only Solutol HS15) was less prone to breaking down after the freezing, as no complete phase separation was observed. The results obtained using an emulsifier mixture revealed that a combination of an anionic surfactant (phospholipids) and non-ionic surfactant (PEG-660-12-hydroxy-stearate) improves the emulsion's stability, compared to the emulsion's stability prepared using only a single emulsifier. However, no direct correlation could be found between the accelerated and the long-term stability data.

Centrifugation↗
PubMed2005

Vegetable oil stability at elevated temperatures in the presence of ferric stearate and ferrous octanoate.

The thermoxidative stability of partially hydrogenated soybean oil (PHSBO) was examined after addition of ferric stearate and ferrous octanoate, and then heating the samples at 120, 160, 180, and 200 degrees C. In a second experiment, the effect of iron concentration (ferric stearate) on PHSBO stability was examined at 180 degrees C, and at concentrations of approximately 0.5 and 1.2 mg of added iron/kg PHSBO. Oil samples were heated continuously for 72 h and sampled every 12 h. The acid value, p-anisidine value, color, dielectric constant and the triacylglycerol polymer content of oil samples were compared to oil samples containing no added iron. Generally, the value of each oxidative index increased with (1) an increase in temperature, (2) an increase in heating time, and/or (3) an increase in iron. The results demonstrate that low concentrations of iron will substantially increase the rate of oxidation for vegetable oil samples heated to temperatures of 120 degrees C to 200 degrees C.

Caprylates↗
PubMed1997

Studies on neurosteroids. V: Separation and characterization of pregnenolone 3-stearate in rat brains using high-performance liquid chromatography.

The separation and characterization of pregnenolone 3-stearate in rat brains are carried out using high-performance liquid chromatography (HPLC). The pregnenolone 3-stearate is obtained from a whole rat brain by extraction with ethyl acetate followed by silica gel column chromatography. The obtained fraction is derivatized with 1-dimethylaminonaphthalene-5-sulfonylhydrazine (dansylhydrazine) or 4-(N,N-dimethylaminosulfonyl)-7-hydrazino- 2,1,3-benzoxadiazole, and the derivative is separated by successive preparative HPLC with fluorescence detection. The chromatographic behaviors of both derivatives are identical to those of authentic samples. The former derivative obtained from the rat brain shows satisfactory mass spectral data, and after hydrolysis, dansylpregnenolone is confirmed by HPLC.

Animals↗
PubMed1979

Effect of food on absorption of erythromycin. A study of two derivatives, the stearate and the base.

Two derivatives of erythromycin, the stearate and the enteric-coated base have been given in a cross-over study to both fasting and non-fasting volunteers. The stearate gave higher plasma concentrations in non-fasting than in fasting subjects. The area under the curve was significantly larger during steady state day 7 than after a single dose. The base showed larger individual variations in concentrations. The release of the drug from the enteric-coated tablets was depressed by food, but the absorption was not prevented.

Adult↗
PubMed1990

Studies on sucrose-palmitate-stearate-containing vesicles encapsulating the cytostatic drug methylglyoxal-bis-guanyl-hydrazone.

Vesicles prepared from sucrose-palmitate-stearate and cholesterol encapsulating the anticancer drug methylglyoxal-bis-guanylhydrazone, were investigated. Treatment with drug-loaded vesicles of this composition in a q.d. 1-4 schedule resulted for murine leukemias P388 in nearly the same increase in life span as the corresponding dose of the free drug. Even very high dosages of sucrose-palmitase-stearate (up to 480 mg.kg-1.d-1) were tolerated by mice.

Animals↗
PubMed1989

The influence of mono(2-ethylhexyl) phthalate and stearates on the migration in soft polyvinyl chloride infusion fluid bags.

The influence of mono(2-ethylhexyl) phthalate (MEHP) and stearates on the migration of di(2-ethylhexyl) phthalate (DEHP) and epoxidized vegetable oils (EVO) in soft polyvinyl chloride infusion fluid bags during agitation has been investigated by gas-liquid chromatography. Normal saline, isotonic glucose and Ringer acetate from 3 different manufacturers were investigated. A covariation was observed between the MEHP concentration in the solution and the pH. The MEHP concentration was not influenced by agitation. There was no correlation between the MEHP concentration in the solution and the migration of EVO and DEHP, or between the stearate concentration and the EVO and DEHP migration.

Chemistry, Pharmaceutical↗
PubMed2000

Elemental and morphological identification of third-body particulate and calcium stearate inclusions in polyethylene components.

Third-body particulate such as human bone chips, hydroxyapatite, and bone cement are considered contributing factors in accelerated wear in total joint replacement. Particulate wear debris is now considered the major contributing factor in aseptic loosening of total joint replacements. The ability to distinguish between different third-body particulate is necessary to better understand wear mechanisms when conducting implant retrieval analysis. The objective of this investigation is to demonstrate that backscattered electron imaging with correlated energy dispersive X-ray analysis can accurately identify third-body particulate in retrieved polyethylene components. It is important that this technique can also distinguish between third-body particulate and normal inclusions in the polyethylene such as calcium stearate, based on the distinct morphology and elemental composition of each material. Therefore, the ability to distinguish third-body particulate from calcium stearate inclusions is essential in gaining a better understanding of the contributing factors associated with coating separation and accelerated wear observed in clinically retrieved polyethylene components.

Biocompatible Materials↗
PubMed1999

Effect of molecular weight, calcium stearate, and sterilization methods on the wear of ultra high molecular weight polyethylene acetabular cups in a hip joint simulator.

Orthopaedic surgeons must currently choose from several types of ultra high molecular weight polyethylene acetabular cups that differ in their material properties and in the methods used for their sterilization. Information on the wear resistance of these different cups may help in the selection process. This study included two separate tests for wear run on a hip simulator to investigate the effect of molecular weight, calcium stearate, and sterilization methods on the wear resistance of ultra high molecular weight polyethylene acetabular cups. Test 1 revealed nearly identical wear rates for acetabular cups with molecular weights in two distinct ranges, as well as for cups with molecular weights in the same range but with or without calcium stearate added. In Test 2, cups that were sterilized in air with gamma irradiation exhibited lower rates of wear than those sterilized with ethylene oxide, presumably due to the crosslinking induced by the irradiation. In addition, cups that were irradiated while packed in a partial vacuum to minimize oxygen absorbed in the surface layer initially showed lower rates of wear than those irradiated in air, with the wear rates becoming similar as wear penetrated the more oxidized surface layer and the more crosslinked subsurface region. Because these tests were run a few months after the irradiation, the potential effects of long-term oxidation of any residual free radicals in the irradiated materials could not be taken into account. After artificial aging to accelerate oxidative degradation of the materials, the wear rates could be markedly different. Analyses performed after wear indicated that the irradiated (i.e., crosslinked) cups exhibited a smaller proportion of, as well as shorter, fibrils in the wear debris and an increased crystallinity and melting temperature and that gamma irradiation in the low-oxygen environment reduced the level of oxidation and increased the level of crosslinking in the surface region of the cups.

Acetabulum↗