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At least 19 recordsLinked to original sources
PubMed1980

[Viscoelastic behaviour of inlay waxes (part 1). Physical and dynamic viscoelastic properties of several raw material waxes (author's transl)].

Several raw material waxes used in the inlay waxes, such as paraffins, carnauba wax, beeswax and dammar were investigated by measurements of X-ray diffraction, dilatometry, differential thermal analysis and dynamic viscoelasticity. The relationships between the viscoelastic behaviour and the physical properties of these waxes were discussed. The solid-solid phase transition from orthorhombic to hexagonal occurred in paraffins and the difference of the crystal transition temperature was observed between the kinds of paraffins. The viscoelastic properties and the thermal expansion of paraffins changed considerably in the crystal transition temperature region. Carnauba wax was an orthorhombic material, but such a crystal transition as paraffins did not appear. The dynamic modules of carnauba wax was greater than that of paraffin and decreased slowly to 70 degrees C and the loss tangent was small in this region. It was found, therefore, that carnauba wax had an elastic property in the crystal transition region of paraffin. Beeswax was also an orthorhombic material. The dynamic modulus of this was smallest in these waxes and the loss tangent increased relatively slowly with increases in temperature. Dammar was an amorphous solid. The dynamic modulus and the loss tangent were approximately constant in the low temperature region and changed greatly in the glass transition region. The thermal expansion of dammar was smallest in these waxes.

Bees↗
PubMed1981

[Viscoelastic behaviour of inlay waxes. (Part 3) Dynamic viscoelastic properties of ternary and quaternary mixtures of waxes (author's transl)].

The viscoelastic properties of ternary and quaternary mixtures added carnauba wax, dammar and beeswax to paraffin were investigated by measurement of dynamic viscoelasticity. The effects of the composition of waxes and the crystal transition temperature of paraffin to the viscoelastic behaviour of these waxes were discussed. The viscoelastic properties of ternary mixtures added carnauba wax and dammar to paraffin were similar to these of binary mixtures for paraffin and dammar in the region of lower temperatures, and similar to these of binary mixtures for paraffin and carnauba wax in the region of higher temperatures. In quaternary mixtures added carnauba wax, dammar and beeswax, tan delta was larger than that of ternary mixtures, so the effect of additions of dammar was disappeared in the region of lower temperatures. Additions of carnauba wax, like to the case of ternary mixtures, had an effect on the viscoelastic properties of quaternary mixtures, but the temperature dependence of G' and tan delta of these waxes were slightly broader than that of ternary mixtures in the region of higher temperature. For a same composition in ternary and quaternary mixtures, even if the paraffins with different transition temperature were used, the shapes of curves of G' and tan delta were so similar to one another that were approximately superposable.

Elasticity↗
PubMed1977

Arthritogenicity of wax D from various mycobacteria related to oil vehicle composition and to the combination with poly I:C, cord factor and acetylated wax D.

Most of wax D (peptidoglycolipid) used here appeared to be ineffective for production of arthritis when given in a water-in-oil emulsion, while the same wax D in squalane was very effective for production of arthritis. Arlacel A as an emulsifier appeared to suppress the arthritogenicity of wax D in squalane, probably through some interaction with the arthritogenic portion of wax D. Poly 1:C seemed to remarkedly enhance the arthritogenicity of wax D, even in water-in-oil emulsion. Acetylated wax D and cord factor (trehalsoe-dimycolate) were much less effective than poly 1:C. Delayed skin hypersensitivity to PPD, peptidoglycan and poly 1:C was also remarkedly affected by oil composition. However, there was no correlation between these delayed hypersensitivities and development of arthritis.

Adjuvants, Immunologic↗
PubMed2000

Purification of a jojoba embryo wax synthase, cloning of its cDNA, and production of high levels of wax in seeds of transgenic arabidopsis.

Wax synthase (WS, fatty acyl-coenzyme A [coA]: fatty alcohol acyltransferase) catalyzes the final step in the synthesis of linear esters (waxes) that accumulate in seeds of jojoba (Simmondsia chinensis). We have characterized and partially purified this enzyme from developing jojoba embryos. A protein whose presence correlated with WS activity during chromatographic fractionation was identified and a cDNA encoding that protein was cloned. Seed-specific expression of the cDNA in transgenic Arabidopsis conferred high levels of WS activity on developing embryos from those plants. The WS sequence has significant homology with several Arabidopsis open reading frames of unknown function. Wax production in jojoba requires, in addition to WS, a fatty acyl-CoA reductase (FAR) and an efficient fatty acid elongase system that forms the substrates preferred by the FAR. We have expressed the jojoba WS cDNA in Arabidopsis in combination with cDNAs encoding the jojoba FAR and a beta-ketoacyl-CoA synthase (a component of fatty acid elongase) from Lunaria annua. (13)C-Nuclear magnetic resonance analysis of pooled whole seeds from transgenic plants indicated that as many as 49% of the oil molecules in the seeds were waxes. Gas chromatography analysis of transmethylated oil from individual seeds suggested that wax levels may represent up to 70% (by weight) of the oil present in those seeds.

Acyltransferases↗
PubMed2001

Release from or through a wax matrix system. I. Basic release properties of the wax matrix system.

Release properties from a wax matrix tablet was examined. To obtain basic release properties, the wax matrix tablet was prepared from a physical mixture of drug and wax powder (hydrogenated caster oil) at a fixed mixing ratio. Properties of release from the single flat-faced surface or curved side surface of the wax matrix tablet were examined. The applicability of the square-root time law and of Higuchi equations was confirmed. The release rate constant obtained as g/min(1/2) changed with the release direction. However, the release rate constant obtained as g/cm2 x min(1/2) was almost the same. Hence it was suggested that the release property was almost the same and the wax matrix structure was uniform independent of release surface or direction at a fixed mixing ratio. However, these equations could not explain the entire release process. The applicability of a semilogarithmic equation was not as good compared with the square-root time law or Higuchi equation. However, it was revealed that the semilogarithmic equation was available to simulate the entire release process, even though the fit was somewhat poor. Hence it was suggested that the semilogarithmic equation was sufficient to describe the release process. The release rate constant was varied with release direction. However, these release rate constants were expressed by a function of the effective surface area and initial amount, independent of the release direction.

Algorithms↗
PubMed2002

Release from or through a wax matrix system. II. Basic properties of release from or through the wax matrix layer.

In order to examine basic properties of release from and through wax matrix layer, reservoir device matrix tablet was prepared from a physical mixture of hydrogenated caster oil and drug that was the same one in the reservoir. Release process could be divided into two stages. The first stage was the formation process of water channel by dissolving the drug in the wax matrix layer, and dissolved drug was released from the matrix layer following the square-root-of-time law equation. Hence, the drug penetration coefficient and tortuosity in the matrix layer were estimated. The second stage was the zero order release process of drug in the reservoir through the wax matrix layer. The release rate constant was calculated from the slope of line. Hence, the drug permeability coefficient and tortuosity were estimated. Fundamentally, tortuosity can not be expressed by some meaningful factors, and is obtained as an experimental result. By preparing wax matrix system from a physical mixture other than melted granule method, it was suggested that the matrix structure was uniform three-dimensionally. As a result, tortuosity could be expressed by a function of porosity, because unrecognized factors such as the surface coverage and thickness of melted wax on the soluble component should not be involved.

Drug Delivery Systems↗
PubMed1977

[Rheological studies on deformation for dental waxes. 2. Stress relaxation behavior of inlay wax (author's transl)].

The rheological properties of inlay wax were investigated by experiment of stress relaxation, thermal expansion, thermal analysis and X-ray diffraction. The results obtained were as follows. The solid-solid phase transition caused by phase transition of paraffin was observed. The stress relaxation curves of inlay wax were obtained at various temperature, and from these curves the stress relaxation master curve was composed by application of time-temperature superposition principle. The temperature dependence of sift factor was devided into two regions of Arrhenius type, and the activation energy was about 60 kcal/mol at the temperature lower than 23 degrees C and 120 kcal/mol at higher temperature. This fact suggests that the relaxation mechanism of inlay wax can be classified into two different modes. The relaxation mechanism at lower temperature region is explained by crystalline relaxation, and at higher temperature is considered to depend upon the solid-solid phase transition process of inlay wax. Calculating from the activation energy, for each 2 degrees C rise in temperature, the rate of rheological change for inlay wax is approximately two-fold at lower temperature region, and about four-fold at higher temperature region.

Elasticity↗
PubMed1981

[Viscoelastic behaviour of inlay waxes. (Part 2) Physical and dynamic viscoelastic properties for binary mixtures of waxes (author's transl)].

Binary mixtures of waxes added carnauba wax, beeswax or dammar to paraffin were investigated by measurements of X-ray diffraction, dilatometry, differential thermal analysis and dynamic viscoelasticity. The relationships between the viscoelastic behaviour and the physical properties of these waxes were discussed. Additions of carnauba wax to paraffin changed drastically viscoelastic properties of paraffin, that is, increased the dynamic modulus, G', and decreased the loss tangent, tan delta, in the region of higher temperatures including the crystal transition temperature region of paraffin. The possible explanation for this change of viscoelastic properties is that the presence of crystals of carnauba wax composed of longer chain molecules than that of paraffin rises interfacial interaction. The temperature dependence of viscoelastic properties for binary mixtures of paraffin and beeswax was approximately the same as that of paraffin. This is because paraffin and beeswax may form a sort of homogeneous phases. Additions of dammar to paraffin increased the elasticity of paraffin in the region of lower temperatures, but did not effected to change of G' and tan delta in the region of higher temperatures. Another effect of additions of dammar was to lower the thermal expansion of binary mixtures.

Elasticity↗
PubMed1978

Sustained release from inert wax matrixes I: drug-wax combinations.

The melting and energy characteristics of several drug-wax combinations were investigated using differential scanning calorimetry. The phase diagrams of binary mixtures of tripelennamine hydrochloride and tolazoline hydrochloride with carnauba wax and castor wax showed no eutectic formation and gave no indication that a significant interaction was involved. However, in tripelennamine mixtures, a slight depression in the drug melting point was observed at around 50% concentration. For ternary systems, i.e., drug, carnauba wax, and stearyl alcohol, thermograms of samples prepared by a fusion method differed slightly from those obtained with mixtures formulated by dissolving all ingredients in chloroform and evaporating the solvent. However, the location of the peak of each component remained essentially the same. A plot of melting point versus concentration of each compound showed insignificant changes in melting point and indicated that no interaction was occurring. The phase diagrams suggested that the combinations are strictly physical and that it is the physical characteristics, such as the hardness and composition of the core and drug particle size, that influence the release or dissolution of drug from the waxy matrix.

Chemistry, Pharmaceutical↗
PubMed1989

Wax lipid secretion and ultrastructural development in the egg-waxing (Gene's) organ in ixodid ticks.

Gene's organ, the egg-waxing organ of ticks, performs an essential function in females by coating the eggs with a waterproofing layer during oviposition, which prevents desiccation of the embryo, ensuring its viability. The organ is a target for control agents and a potential site of virus replication involving trans-oval transmission of arboviruses. The organ is a complex dermal gland, developed to an elaborate degree. The external appendage, the horns, is an evertable balloon-like cuticular sac which manipulates the eggs and coats them in wax. Wax passes through pores in the cuticle from the internal, sub-cuticular lumen. Gene's organ develops in synchrony with oogenesis and oviposition. This paper describes the development of the gland cells and formation of the intra-cuticular lumen and its ultrastructure during engorgement and oviposition in ixodid ticks. The structural basis for wax secretion in Gene's organ is also described.

Animals↗
PubMed2002

Release from or through a wax matrix system. III. Basic properties of release through the wax matrix layer.

Release property of reservoir device matrix tablet was examined. Wax matrix layer was prepared from physical mixture of lactose and hydrogenated castor oil to obtain basic release properties. Release process showed zero order kinetics in a steady state after a given lag times, and could be divided into two stages. The first stage was the formation process of water channel by dissolving the soluble component in the wax matrix layer. The lag time was considered to be the time required forming water channel and the time begun to release drug through the wax matrix layer at the same time. The lag time obtained by applying the square root law equation was well connected with the amount of matrix layer and mixed weight fraction of component in matrix layer. The second stage was the zero order release process of drug in the reservoir through the wax matrix layer. The release rate constants were calculated by taking into accounts of the thickness of matrix layer and permeability coefficient, and were well connected with the amount of matrix layer and mixed weight fraction of component. Also it was suggested that the tortuosity of matrix layer could be expressed by a function of the porosity defined by the mixed weight fraction.

Chemistry, Pharmaceutical↗
PubMed2003

Release from or through a wax matrix system. V. Applicability of the square-root time law equation for release from a wax matrix tablet.

To obtain basic and clear release properties, wax matrix tablets were prepared from a physical mixture of drug and wax powder at a fixed mixing ratio. Properties of release from the single flat-faced surface, curved side surface, and/or whole surface of the wax matrix tablet were examined. Then tortuosity and the applicability of Higuchi's square-root time law equation were examined. The Higuchi equation well analyzed the release processes of different release manners. However, the region fitted to the Higuchi equation differed with the release manner. Tortuosity obtained with release from the single flat-faced surface and curved side surface was comparable with that obtained with the release from a reservoir device tablet, whereas tortuosity obtained with release from the whole surface was larger. As the wax matrix tablets were prepared at a fixed mixing ratio, their internal structures should be similar. Therefore changes in the matrix volume or volume fraction with release were examined, and an extra volume where dissolved drug stray becomes large with release time in the case of release from the whole surface. These factors should be taken into account for evaluation of applicability and release properties. Furthermore, the entire release process should be analyzed using a combination of the square-root time law and other suitable equations in accordance with release manner or condition.

Tablets↗
PubMed2002

A novel bifunctional wax ester synthase/acyl-CoA:diacylglycerol acyltransferase mediates wax ester and triacylglycerol biosynthesis in Acinetobacter calcoaceticus ADP1.

Triacylglycerols (TAGs) and wax esters are neutral lipids with considerable importance for dietetic, technical, cosmetic, and pharmaceutical applications. Acinetobacter calcoaceticus ADP1 accumulates wax esters and TAGs as intracellular storage lipids. We describe here the identification of a bifunctional enzyme from this bacterium exhibiting acyl-CoA:fatty alcohol acyltransferase (wax ester synthase, WS) as well as acyl-CoA:diacylglycerol acyltransferase (DGAT) activity. Experiments with a knock-out mutant demonstrated the key role of the bifunctional WS/DGAT for biosynthesis of both storage lipids in A. calcoaceticus. This novel type of long-chain acyl-CoA acyltransferase is not related to known acyltransferases including the WS from jojoba (Simmondsia chinensis), the DGAT1 or DGAT2 families present in yeast, plants, and animals, and the phospholipid:diacylglycerol acyltransferase catalyzing TAG formation in yeast and plants. A large number of WS/DGAT-related proteins were identified in Mycobacterium and Arabidopsis thaliana indicating an important function of these proteins. WS and DGAT activity was demonstrated for the translational product of one WS/DGAT homologous gene from M. smegmatis mc(2)155. The potential of WS/DGAT to establish novel processes for biotechnological production of jojoba-like wax esters was demonstrated by heterologous expression in recombinant Pseudomonas citronellolis. The potential of WS/DGAT as a selective therapeutic target of mycobacterial infections is discussed.

Acinetobacter↗
PubMed1981

Mechanism of the anisotropic dimensional change of the wax pattern prepared by the softened wax technique. (1) Relationship between recovery and crystal orientation.

In order to obtain information on the behavior of wax pattern distortion and to reveal its mechanism, the following experiments have been conducted: measurements of fundamental properties including distribution of molecular weight, crystal structure, phase transition, and viscosity, and investigation of the crystal orientation and recovery phenomena. If the wax is deformed plastically at higher temperatures, transformation appears to be a smooth transition from an isotropic distribution of the crystal orientation to an arranged structure. In the case of uniaxial compression, the c-axes are rearranged parallel to the compressed direction and the b-axes and a-axes are randomly oriented in the plane normal to the c-axes. This preferred orientation is due to the crystal rotation. The degree of preferred orientation increases with the increase in compression ratio over all temperatures between 35 degrees C and 55 degrees C. Above 45 degrees C, the degree of orientation decreases with an increase in temperature despite the equal compression ratio. From this fact, the degree of orientation is associated with the crystallinity at deformation temperatures as well as the degree of deformation. The preferentially oriented specimen expands greatly in the direction parallel to the molecular chain axis and shrinks to a great extent in the direction perpendicular to the chain axis. This anisotropy is caused mainly by the recovery. Moreover, the extent of recovery is associated closely with the degree of the preferred orientation. The dimensional change due to the recovery is extraordinarily large (30 to 40%) in comparison with the normal thermal expansion from room temperature to 45 degrees C (approximately 1.2%). This large extent of recovery is explained by the rubber-like deformation in the amorphous region.

Crystallization↗