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At least 145 records · Page 8Linked to original sources
PubMed2006

Chemical composition of epicuticular wax crystals on the slippery zone in pitchers of five Nepenthes species and hybrids.

Plants of the carnivorous genus Nepenthes efficiently trap insects in leaf pitchers, mostly employing epicuticular wax crystals on the pitcher walls to make them slippery for the prey. In the present study, the compositions and micromorphologies of the wax crystals of five Nepenthes species and hybrids were analysed in order to test whether the chemical principles underlying this ecological function are widespread within the genus. Three wax layers could be distinguished within the Nepenthes pitcher cuticles: (1) the outermost part of the crystals forming the platelets visible in standard scanning electron microscopy, (2) the bottom portion of the epicuticular wax crystals, and (3) an intracuticular wax layer. The composition of the intracuticular wax differed significantly from that of the neighbouring epicuticular layer. The compositions of corresponding wax mixtures from all five Nepenthes species and hybrids were very similar, with almost equal amounts of very long chain aldehydes and primary alcohols. While triacontanal (C(30) aldehyde) was prevailing in the epicuticular crystals of Nepenthes albomarginata and Nepenthes x intermedia, Nepenthes x superba and Nepenthes x henriana were found to have especially high percentages of dotriacontanal (C(32) aldehyde). Nepenthes "khasiana" had an intermediate aldehyde composition with almost equal amounts of both chain lengths.

Caryophyllaceae↗
PubMed2005

Surface composition of myrmecophilic plants: cuticular wax and glandular trichomes on leaves of Macaranga tanarius.

Primary plant surfaces, covered with cuticles consisting of cutin and waxes, are important substrates for interaction with insects. The composition of leaf surfaces of the myrmecophilic plant Macaranga tanarius was studied. The prenylated flavanone nymphaeol-C was identified in surface extracts and was localized exclusively in glandular trichomes on the abaxial leaf side. The epidermal pavement cells surrounding these trichomes were covered with a smooth film of epicuticular wax from which few small wax crystals protruded. The epicuticular wax amounted to approximately 8 microg cm(-2), corresponding to 85% of the wax load on the adaxial as well as the abaxial leaf sides. The epicuticular wax mixtures from both leaf surfaces contained more than 70% primary alcohols, 14% fatty acids, 2% aldehydes, and traces of alkyl acetates, with chain lengths ranging from C(20) to C(38). In contrast, the intracuticular wax layer was largely dominated by triterpenoid alcohols alpha-amyrin, beta-amyrin, and lupeol. Consequently, these characteristic compounds are not available for direct contact with insects on the plant surface.

Acetates↗
PubMed2006

Crystallinity of plant epicuticular waxes: electron and X-ray diffraction studies.

The crystal structure of the epicuticular waxes of 35 plant species has been examined by electron diffraction and X-ray powder diffraction. The waxes include the most common morphological wax types such as platelets, tubules, films and rodlets. Most of them were prepared with a special mechanical isolation method, which preserves the original crystal structure. Solvent-extracted recrystallized plant waxes were compared with mechanically isolated samples. The waxes were found to occur in three different crystal structures. Most of the waxes exhibited an orthorhombic structure which is the most common for aliphatic compounds. Tubules containing mainly secondary alcohols showed diffraction reflections of a triclinic phase; broad reflection peaks indicated a significant disorder. Ketones, in particular beta-diketone tubules, displayed the reflections of a hexagonal structure. Mixtures of different phases could be identified. For most of the waxes, the 'long spacing' diffraction reflections indicated a layer structure with the characteristics of the major component. Others showed no 'long spacing' reflections indicating a strong disorder of the molecular layers.

Crystallization↗
PubMed2000

Waxes and lipids associated with the external waxy structures of nymphs and pupae of the giant whitefly, Aleurodicus dugesii.

The nymphs and pupae of the giant whitefly, Aleurodicus dugesii, produce large quantities of external lipids, both as waxy particles and as waxy filaments. The nymphs and pupae extrude filaments from two dorsal rows of five pores each. Filaments can attain lengths of 5-8 cm. The external lipids of nymphs and pupae consist largely of long-chain aldehydes, alcohols, acetate esters and wax esters. Hydrocarbons are minor components. Soon after hatching, the nymph produced an unidentified waxy fringe extruded laterally from its margin. After molting to the second instar, long, hollow, waxy filaments were produced by the immature stages. The major lipid class associated with the filaments was saturated wax esters (89%), mainly C44, C46 and C60. Associated with formation of the filaments were waxy particles in the shape of curls, which peeled off of the extruding filaments. Similar but more tubular-shaped curls were also produced by numerous lateral pores so that, eventually, the curls completely camouflaged the nymph. The major lipid class of the curls was wax esters (50%), mainly C44 and C46. The cuticular surface lipids of the nymphs were mainly long-chain aldehydes (43%) and wax esters (27%). Unsaturated fatty acid moieties constituted 2 and 19% of the wax esters of curls and nymph cuticular surface lipids, respectively. The major lipid classes of pupae and of their palisade were long-chain aldehydes and alcohols. No unsaturated wax esters were detected in the filaments, but 30% of pupal and 21% of palisade surface wax esters were unsaturated in their fatty acid moieties, 16:1, 18:1 and 20:1.

Animals↗
PubMed2004

Effect of the epicuticular waxes of fruits and vegetables on the photodegradation of rotenone.

The effect of epicuticular waxes extracted from fruits (apple, nectarine, pear, and plum) and vegetables (tomato and eggplant) on the photodegradation of rotenone was studied. The waxes affected the decay rate and the degradation pathway of this botanical insecticide. Tomato, nectarine, and plum waxes decreased the photodegradation rate compared to controls, whereas apple and pear waxes increased it. Rotenone irradiated under sunlight without waxes gave seven photoproducts; in contrast, in the presence of waxes it changed its behavior, leading to different pathways according to the wax employed. The main photoproduct formed was 12abeta-rotenolone.

Fruit↗
PubMed1991

Development and evaluation of sustained-release ibuprofen-wax microspheres. I. Effect of formulation variables on physical characteristics.

A congealable disperse phase encapsulation method was used to prepare sustained-release ibuprofen-wax microspheres. Microspheres prepared with paraffin wax, such as ceresine and microcrystalline waxes, using polyvinylpyrrolidone (PVP) as dispersant had a tendency to aggregate, but the addition of wax modifiers (stearyl alcohol and glyceryl monostearate) greatly reduced aggregation. Optimum modifier and dispersant concentrations were 20% (w/w) and 5% (w/v), respectively. The particle size distribution of the microspheres was log-normal. An increase in modifier, dispersant concentration, emulsification stirring speed, or temperature shifted the size distribution toward finer particles. Microcrystalline wax required a higher emulsification temperature and produced finer particles than ozokerite wax. The recovery of drug from the different microsphere formulations varied between 71 and 92%. Differential scanning calorimetry (DSC) of the single components and physical mixtures showed endothermic peaks at the respective melting-point ranges. The DSC of the ceresine and microcrystalline wax microspheres was similar to rescans of ternary mixtures of components of the microspheres with less prominent and lower melting temperatures than individual components or physical mixtures.

Delayed-Action Preparations↗
PubMed2004

Monoterpenes and epicuticular waxes help female autumn gum moth differentiate between waxy and glossy Eucalyptus and leaves of different ages.

The autumn gum moth, Mnesampela privata, is a native Australian species whose preferred host, Eucalyptus globulus (Myrtaceae), is an aromatic evergreen tree that has long-lived waxy leaves during the juvenile phase of growth. We compared the behavioral and antennal responses of female moths to whole leaves (new and old) and samples of foliar chemicals (from new and old leaves) from a typical E. globulus subsp. pseudoglobulus with responses to a glossy, half-sibling E. g. subsp. pseudoglobulus putative hybrid (the result of natural cross-pollination). We also studied larval survival and development on leaves from the same trees. In laboratory binary-choice assays, female M. privata laid more eggs on waxy leaves than on glossy leaves thereby confirming the nonpreference for the glossy tree that was observed in the field. Analyses of the monoterpenes and waxes of both trees revealed that they had comparable suites of monoterpenes and total oil contents but different suites of epicuticular waxes. Headspace extracts differed in the intensity of component monoterpenes. Gas chromatographic analyses with electroantennographic detection showed different patterns of monoterpene detection. Leaves of the glossy tree had a less diverse array of epicuticular waxes than those of the waxy tree. Electroantennographic screening of responses to wax extracts from leaves (new and old) from either tree revealed positive dose-dependent responses of female antennae to waxes from new leaves only. Binary-choice assays also revealed a strong preference by ovipositing females for new, compared to old, leaves whether they were from the waxy or the glossy tree. However, new leaves from either tree could be manipulated (by physical abrasion of epicuticular waxes) so that females would lay almost no eggs on them. Larval survival did not differ between groups reared on leaves from both trees (new and old). Over 70% of all larvae survived to pupation. However, larvae reared on leaves from the glossy tree took longer to pupate than those reared on leaves from the waxy tree. Also, larvae reared on new leaves from either tree did not perform as well as those reared on old leaves. Monoterpene and wax cues are suggested as helping female M. privata locate preferred hosts in native forests.

Animals↗
PubMed2001

Chemical composition of the Prunus laurocerasus leaf surface. Dynamic changes of the epicuticular wax film during leaf development.

The seasonal development of adaxial Prunus laurocerasus leaf surfaces was studied using newly developed methods for the mechanical removal of epicuticular waxes. During epidermal cell expansion, more than 50 microg leaf(-1) of alkyl acetates accumulated within 10 d, forming an epicuticular wax film approximately 30 nm thick. Then, alcohols dominated for 18 d of leaf development, before alkanes accumulated in an epicuticular wax film with steadily increasing thickness (approximately 60 nm after 60 d), accompanied by small amounts of fatty acids, aldehydes, and alkyl esters. In contrast, the intracuticular waxes stayed fairly constant during development, being dominated by triterpenoids that could not be detected in the epicuticular waxes. The accumulation rates of all cuticular components are indicative for spontaneous segregation of intra- and epicuticular fractions during diffusional transport within the cuticle. This is the first report quantifying the loss of individual compound classes (acetates and alcohols) from the epicuticular wax mixture. Experiments with isolated epicuticular films showed that neither chemical conversion within the epicuticular film nor erosion/evaporation of wax constituents could account for this effect. Instead, transport of epicuticular compounds back into the tissue seems likely. Possible ecological and physiological functions of the coordinate changes in the composition of the plant surface layers are discussed.

Biological Transport↗
PubMed1985

Proportions of various straight and branched fatty acid chain types in the sebaceous wax esters of young children.

The fatty acid composition of sebaceous wax esters was examined in 20 children, ages 6-8, using quartz capillary gas chromatography. The results were compared with a previously reported study of wax ester composition in 10 adults, in which the same analytical techniques were used. The children's wax esters showed more variability in the proportions of all fatty acid chain types than was found in adults. The most striking difference between the 2 age groups was in the proportions of iso-branched fatty acids with odd numbers of carbon atoms. These ranged from 1-26% of fatty acids in the children's wax esters but were not more than 3% of fatty acids in the adults' wax esters. Some of the variability in wax ester fatty acid composition in children seemed to be related to variation in rates of sebum production. The highest percentages of terminally branched (iso-even, iso-odd, and anteiso) and the lowest percentages of internally branched fatty acids were found in the children with the lowest rates of sebum secretion. However, even in children with similar rates of sebum secretion there were considerable differences in wax ester fatty acid composition, especially with respect to iso-even fatty acids. The results suggest that sebum fatty acid composition is influenced both by genetic factors and by limitations on the supply of precursors for terminally branched, but not internally branched, fatty acids.

Adult↗
PubMed1969

Wax D fraction of an unclassified Mycobacterium strain.

Wax D prepared from the P-6 strain of the scotochromogenic species of Mycobacterium scrofulaceum constituted 0.3% of the dry bacilli. In the acid hydrolysates, alanine, glutamic acid, glycine, and mesodiaminopimelic acid were found as amino acid constituents. Mannose, galactose, and glucosamine were detected by paper chromatography. However, arabinose could not be detected. The quantity of hexosamine was 0.2 to 0.3%. Wax D of P-6 was found to be adjuvant-active, as revealed by a positive corneal reaction. The antigenicity of wax D of P-6 was shown by the agglutination reaction between the suspension of wax D and the anti-wax D antiserum. Periodate oxidation of the hydrosoluble portion reduced the inhibitory effect of the hydrosoluble portion on agglutination of the suspension of wax D. The light fraction of wax D had a peptide portion consisting of alanine, glutamic acid, glycine, and diaminopimelic acid and was found to be adjuvant-active in an amount of 1,000 mug.

Agglutination Tests↗
PubMed2001

Is Bone-wax an injectable urologic material?

OBJECTIVE: Injection of endoscopic material for reflux and incontinence therapies became popular in urology because of its simplicity and repeatability. Research is going on to develop an ideal injectable material. In this experimental study we investigated whether the bone wax used for osteotomy hemostasis in orthopedic and neurosurgical operations could be used as an injectable material. MATERIALS AND METHODS: A total of 20 rabbits were included in the study: 6 underwent a sham operation, and in the remaining 14 rabbits, 0.5 ml bone wax liquefied with n-butyl acetic acid was injected submucosally via a 20-gauge needle at three different points on the anterior bladder wall. Cystectomy was performed on the 15th day in 2 rabbits (group I), on the 60th day in 2 (group II) and on the 150th day in 10 (group III). 0.20 ml bone wax was also injected subcutaneously and intramuscularly 7 days before cystectomy in group III. Bladders were examined macroscopically and histopathologically. All animals' lungs, livers, kidneys, spleens and brains were also removed and examined histologically. RESULTS: Submucosal swellings of bone wax maintained their localizations and shapes in all groups and all of the 42 bone-wax injection sites could be easily identified. Histologically, slight edema around the implant was seen in group I. In group II, collagen was increased around the implants and minimal hyperplasia of the epithelium overlaying bone wax was noted. 150 days after the injections, moderate collagen production and a mild increase in vascularity were seen around the implants. There was no macroscopic or microscopic evidence that implants migrated to locations other than the injection sites. CONCLUSIONS: When injected to the bladder submucosa, bone wax seems to be inert and biocompatible, encouraging further research to develop it as an alternative agent in the endoscopic treatment of vesicoureteral reflux and sphincteric incontinence.

Animals↗
PubMed2006

Partial least squares regression calibration for determining wax content in processed flax fiber by near-infrared spectroscopy.

The quality of flax fiber in the textile industry is closely related to the wax content remaining on the fiber after the cleaning process. Extraction by organic solvents, which is currently used for determining wax content, is very time consuming and produces chemical waste. In this study, near-infrared (NIR) spectroscopy was used as a rapid analytical technique to develop models for wax content associated with flax fiber. Calibration samples (n=11) were prepared by manually mixing dewaxed fiber and isolated wax to provide a range of wax content from 0 to 5%. A total of fourteen flax fiber samples obtained after a cleaning process were used for prediction. Principal component analysis demonstrated that one principal component is enough to separate the flax fibers by their wax content. The most highly correlated wavelengths were 2312, 2352, 1732, and 1766 nm, in order of significance. Partial least squares models were developed with various chemometric preprocessing approaches to obtain the best model performance. Two models, one using the entire region (1100-2498 nm) and the other using the selected wavelengths, were developed and the accuracies compared. For the model using the entire region, the correlation coefficient (R2) between actual and predicted values was 0.996 and the standard error of prediction (RMSEP) was 0.289%. For the selected-wavelengths model, the R2 was 0.997 and RMSEP was 0.272%. The results suggested that NIR spectroscopy can be used to determine wax content in very clean flax fiber and that development of a low-cost device, using few wavelengths, should be possible.

Calibration↗
PubMed2001

Chemical and physical analyses of wax ester properties.

Wax esters are major constituents of the surface lipids in many terrestrial arthropods, but their study is complicated by their diversity. We developed a procedure for quantifying isomers in mixtures of straight-chain saturated and unsaturated wax esters having the same molecular weights, using single-ion monitoring of the total ion current data from gas chromatography-mass spectrometry. We examined the biological consequences of structural differences by measuring the melting temperatures, T(m), of >60 synthetic wax esters, containing 26-48 carbon atoms. Compounds containing saturated alcohol and acid moieties melted at 38-73 degrees C. The main factor affecting T(m) was the total chain length of the wax ester, but the placement of the ester bond also affected T(m). Insertion of a double bond into either the alcohol or acid moiety decreased T(m) by approximately 30 degrees C. Simple mixtures of wax esters with n-alkanes melted several degrees C lower than predicted from the melting points of the component lipids. Our results indicate that the wax esters of primary alcohols that are most typically found on the cuticle of terrestrial arthropods occur in a solid state under physiological conditions, thereby conferring greater waterproofing. Wax esters of secondary alcohols, which occur on melanopline grasshoppers, melted >60 degrees C below primary esters of the same molecular weight and reduced T(m) of the total surface lipids to environmental values.

Animals↗
PubMedDate not supplied

Process and formulation variables in the preparation of wax microparticles by a melt dispersion technique. I. Oil-in-water technique for water-insoluble drugs.

Ibuprofen-wax (carnauba, paraffin, beeswax, and the semisynthetic glyceryl esters--Gelucire 64/02 and Precirol ATO5) microparticles were prepared without organic solvents as an alternative to polymeric microparticles. In the melt dispersion technique, the drug-wax melt was emulsified into a heated aqueous phase followed by cooling to form the microparticles. The microparticles were characterized with respect to their drug loading, and morphological and release properties. They were spherical and non-agglomerated and drug loading close to 60 per cent were achieved. The more hydrophilic waxes (Gelucire 64/02 or Precirol ATO5) could be prepared without the use of surfactants. With the other waxes, increasing amounts of sodium lauryl sulphate in the external aqueous phase decreased the drug loading because of drug solubilization when compared to the polymeric stabilizer, poly(vinyl alcohol). The type of wax, the rate of cooling, and the temperature of the aqueous phase had no significant effect on the drug loading because of the low solubility of the drug in the external aqueous phase. The drug release was controlled by the hydrophobicity of the wax. Besides ibuprofen, other water-soluble drugs (ketoprofen, indomethacin, hydrocortisone) were also encapsulated by this method. The wax microparticles could be formulated into an aqueous sustained-release oral suspension dosage form.

Delayed-Action Preparations↗
PubMed2005

Profiling candidate genes involved in wax biosynthesis in Arabidopsis thaliana by microarray analysis.

Plant epidermal wax forms a hydrophobic layer covering aerial plant organs which constitutes a barrier against uncontrolled water loss and biotic stresses. Wax biosynthesis requires the coordinated activity of a large number of enzymes for the formation of saturated very-long-chain fatty acids and their further transformation in several aliphatic compounds. We found in the available database 282 candidate genes that may play a role in wax synthesis, regulation and transport. To identify the most interesting candidates, we measured the level of expression of 204 genes in the aerial parts of 15-day-old Arabidopsis seedlings by performing microarray experiments. We showed that only 25% of the putative candidates were expressed to significant levels in our samples, thus significantly reducing the number of genes which will be worth studying using reverse genetics to demonstrate their involvement in wax accumulation. We identified a beta-keto acyl-CoA synthase gene, At5g43760, which is co-regulated with the wax gene CER6 in a number of conditions and organs. By contrast, we showed that neither the fatty acyl-CoA reductase genes nor the wax synthase genes were expressed in 15-day-old leaves and stems, raising questions about the identity of the enzymes involved in the acyl-reduction pathway that accounts for 20% of the total wax amount.

Acyltransferases↗
PubMed2000

Local information for primary care: the St Albans WAX Project (STAPCIS).

The St. Albans Primary Care Information Service (STAPCIS) is a database of locally focused information designed to be of use for GPs and the Primary Care team as a whole in a particular area. It is currently being used by practices in the St. Albans, Dacorum and Watford & Three Rivers Primary Care Groups. STAPCIS developed from a project initiated in late 1997 to pilot the use of the WAX software to improve access to directory-type and full-text material needed for easy access by primary care staff and traditionally difficult to manage. The database is updated centrally by the STAPCIS Librarian who distributes the new editions to the practices. The WAX software itself was developed by the Cambridge Centre for Clinical Informatics. STAPCIS contains locally and nationally produced relevant information from a variety of sources, including full-text clinical guidelines and directories of Trusts. Decisions on new content are made by a Steering Group and the GPs and Primary Care teams are particularly encouraged to make suggestions regarding new content. The service is financially supported by the three primary care groups. The STAPCIS Librarian is project-managed by the Library & Information Development Unit (North Thames ), which also provides additional equipment and expertise. A new software company, WaX Info Ltd ( ), will soon be releasing a new version of the software, WaX. WaX consists of a WaX client and WaX ActiveLibrary server software. With the new version, the 'books' of information will still be stored on the user's PC, retaining the speed of access, but the server will enable users to 'borrow' books from remote locations and will provide automatic updates of all books. The new software will improve the management and distribution processes of STAPCIS once all of the practices have Internet connectivity.

Community Health Services↗
PubMed1997

Discrepancy in patch test results with wool wax alcohols and Amerchol L-101.

Wondering why Amerchol L-101 (containing wool wax alcohols obtained from the hydrolysis of wool fat) appears as a test material (100%) in a cosmetics series (Chemotechnique Diagnostics AB), as wool wax alcohols were already tested in the European standard series, we added Amerchol L-101 (100%) systematically to the standard series. From 8 April 1991 to 28 February 1992, a total of 393 patients were tested: 3.05% (n = 12) showed positive test results (+, +2, +3) for wool wax alcohols as well as Amerchol L-101 (100%), 0.3% (n = 1) for wool wax alcohols only, and 11.1% (n = 44) for Amerchol L-101 (100%) only. Thus, the positive tests for Amerchol L-101 (100%) had a higher frequency of 3.4 compared to those for wool wax alcohols. In the meantime, we also added Amerchol L-101 50% (Trolab) to the standard series. Of all patients tested (n = 223) 2.7% (n = 6) had positive reactions to wool wax alcohols and 12.1% (n = 27) to Amerchol L-101 100% and/or 50%. Thus, positive reactions to Amerchol L-101 (100% and 50%) were 4.5 higher, whereas the rate of concordancy decreased. It is remarkable that 8 patients only had a positive reaction to Amerchol L-101 50% and 9 only to Amerchol L-101 100%. It seems that we miss many diagnoses in contact allergy by using only the standard wool wax alcohols test (30%).

Adolescent↗
PubMed1996

Effect of selected physical properties of waxes on investments and casting shrinkage.

This study evaluated the relationship between flow characteristics, bending strength, and softening temperature of paraffin and dental inlay waxes to casting shrinkage when patterns were invested with a phosphate-bonded investment. This study found that the casting shrinkage decreased as the flow of the wax pattern increased. If a low flow wax is used or if there is a need for a thick pattern, the size of the casting ring should be increased. When wax patterns are formed for cast restorations, it is important to select the type of wax with the most desirable properties for the margin and the occlusal portions. Moreover, to accurately fabricate castings, it is necessary to understand the physical properties of the chosen waxes.

Chemical Phenomena↗