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PubMed1995

Low-volume application by mist-blower compared with conventional compression sprayer treatment of houses with residual pyrethroid to control the malaria vector Anopheles albimanus in Mexico.

Village-scale trials were carried out in southern Mexico to compare the efficacy of indoor-spraying of the pyrethroid insecticide lambda-cyhalothrin applied either as low-volume (LV) aqueous emulsion or as wettable-powder (WP) aqueous suspension for residual control of the principal coastal malaria vector Anopheles albimanus. Three indoor spray rounds were conducted at 3-month intervals using back-pack mist-blowers to apply lambda-cyhalothrin 12.5 mg a.i./m2 by LV, whereas the WP was applied by conventional compression sprayer at a mean rate of 26.5 mg a.i./m2. Both treatments caused mosquito mortality indoors and outdoors (collected inside house curtains) as a result of contact with treated surfaces before and after feeding, but had no significant impact on overall population density of An. albimanus resting indoors or assessed by human bait collections. Contact bioassays showed that WP and LV treatments with lambda-cyhalothrin were effective for 12-20 weeks (> 75% mortality) without causing excito-repellency. Compared to the WP treatment (8 houses/man/day), LV treatment (25 houses/man/day) was more than 3 times quicker per house, potentially saving 68% of labour costs. This is offset, however, by the much lower unit price of a compression sprayer (e.g. Hudson 'X-pert' at US$120) than a mist-blower (e.g. 'Super Jolly' at US$350), and higher running costs for LV applications. It was calculated, therefore, that LV becomes more economical than WP after 18.8 treatments/100 houses/10 men at equivalent rates of application, or after 7.6 spray rounds with half-rate LV applications.

Animals↗
PubMed1995

dewA encodes a fungal hydrophobin component of the Aspergillus spore wall.

An anonymous cDNA clone, pCAN4, was shown previously to correspond to an mRNA that accumulates preferentially during asexual sporulation of the filamentous fungus Aspergillus nidulans. The peptide encoded by pCAN4 is a fungal hydrophobin, a group of small, hydrophobic cell wall proteins. When the CAN4 gene was disrupted, conidia and conidiophores appeared to be normal, but sporulating colonies wetted more rapidly with detergent solutions than did the wild type. We renamed CAN4 dewA for the detergent wettable phenotype and mapped it to chromosome V, 24 map units from cysC. The A. nidulans rodA gene also encodes a sporulation-specific fungal hydrophobin. Spores of a dewA- rodA- double mutant were less hydrophobic than those of either mutant alone, showing that dewA and rodA contribute independently to spore-wall hydrophobicity. Immunolocalization of DewA by epitope tagging demonstrated that DewA is present in the spore wall, but not in the walls of germ tubes, hyphae or cells of the spore-producing conidiophore. We conclude that dewA encodes a new fungal hydrophobin component of the conidial wall.

Amino Acid Sequence↗
PubMed2006

An evaluation of silicone-hydrogel lenses worn on a daily wear basis.

PURPOSE: To examine the clinical performance of two brands of silicone-hydrogel lenses when worn on a daily wear basis. METHODS: Fifty-six subjects with no ocular disease were enrolled at multiple sites in Australasia. Contact lenses made from galyfilcon A or lotrafilcon A were randomly assigned to each eye of the subject and the lenses were worn on a daily wear basis for a period of two weeks. Subjects did not know the identity of the lenses they wore. Clinical data and patient responses to a questionnaire were gathered at an initial visit and after two weeks of wear. RESULTS: For both lenses, the degree of limbal hyperaemia and bulbar conjunctival hyperaemia decreased significantly over the two-week wearing period. The eyes wearing galyfilcon A lenses showed an increase in conjunctival staining compared to the baseline measures. On average, galyfilcon A lenses decentred more and moved less than the lotrafilcon A lenses. The lotrafilcon A lenses showed a greater loss of wettability, as judged by practitioner grading, than the galyfilcon A lenses over the two-week period. The subjective responses showed strong preference for the galyfilcon A lens across 26 of 27 questions relating to comfort, vision, handling, preference and other subjective outcomes. DISCUSSION: The results show that different silicone-hydrogel lenses have different performance characteristics on the eye, when worn on a daily wear basis. Striving for high oxygen transmissibility at the expense of other properties may lead to a range of undesirable performance characteristics.

Adolescent↗
PubMed1994

New processes for surface treatment of catheters.

Infection, thrombosis, and stenosis are among the most common complications of blood-contacting catheters and are caused by surface properties of the substrate materials. Ion beam-based processes such as ion implantation and ion beam-assisted deposition affect only the outer micron of the treated material surface; there is little effect on bulk properties. These processes were therefore used on common catheter materials, and their biological properties were evaluated. Ion implantation of materials such as silicone rubber resulted in a less tacky, more wettable surface that demonstrated thrombus-resistance in both in vivo and preliminary clinical studies. Ion beam-assisted deposition was used to deposit silver-based coatings, which demonstrated antimicrobial activity in in vitro and clinical studies. Biocompatibility of these processed catheter materials was also demonstrated using simple laboratory studies. These processes, therefore, can be readily applied to blood-contacting catheters to make them thrombus- and infection-resistant.

Catheters, Indwelling↗
PubMed1996

Attachment of bacteria to model solid surfaces: oligo(ethylene glycol) surfaces inhibit bacterial attachment.

Bacterial cell attachment to the surfaces of self-assembled monolayers formed by the adsorption of omega-substituted alkanethiols on transparent gold films has been studied under defined bacterial culture and flow conditions. Phase contrast microscopy was used to quantify the attachment of two organisms, one of medical (Staphylococcus epidermidis) and one of marine (Deleya marina) importance. Self-assembled monolayers terminated with hexa(ethylene glycol), methyl, carboxylic acid and fluorocarbon groups were investigated. Over the range of experimental conditions, self-assembled monolayers formed from HS(CH2)11(OCH2CH2)6OH were found to be uniformly resistant to bacterial attachment, with a 99.7% reduction of attachment for both organisms when compared to the most fouled surface for each organism. On other surfaces, S. epidermidis and D. marina were shown to exhibit very different attachment responses to the wettability of the substratum. While the attachment of S. epidermidis correlated positively with surface hydrophilicity, D. marina showed a preference for hydrophobic surfaces. This study suggests that surfaces incorporating high densities of oligo(ethylene glycol) are good candidates for surfaces that interact minimally with bacteria.

Bacterial Adhesion↗
PubMed1987

Selected methods of investigation for blood-contact surfaces.

It is imperative that operating personnel and regulatory agencies have secure, advance, and accurate knowledge of the true surface properties of materials to be contacted with flowing blood. The actual devices must be characterized in their sterile, immediate pre-exposure states. Although very sensitive electronic instrumental analysis techniques are available, the requirements for small specimens exposed to high vacuums and energetic beams hinder their use with practical prosthetic implants. Thus, it remains important that classical estimation of the "wettability" of nonphysiologic materials by simple contact angle measurements can document their real surface qualities in the condition and environment of their intended application. These data, acquired quickly and nondestructively, together with confirming laboratory results from internal reflection infrared spectroscopy, scanning microscopy, and X-ray analysis, are the most useful indicators of material safety and effectiveness for blood contact uses. Experience has shown that the critical surface tensions of materials, determined from contact angle measurements in air rather than underwater, are generally predictive of the tenacity of bioadhesion at their boundaries with blood and other living tissues. Overall, it is now recommended that the surface chemistry of all implant materials be characterized before any exposure to flowing blood, as a minimum requirement of good practice.

Animals↗
PubMed1979

Effect of disruption of the sebaceous layer of the sheep's skin on the incidence of fleece-rot.

It was postulated that integrity of the sebaceous layer on the skin is important in maintaining resistance to fleece-rot. This hypothesis was tested in an experimenta of a 2 x 2 factorial design in which sebaceous layer disruption and wetting were the 2 treatments. The sebaceous layer was disrupted by applying a light petroleum solvent to the skin of the sheep. Fleece-rot occurred in all sheep (20) that were both wetted and had the sebaceous layer disrupted while 9/19 of those wetted but without the sebaceous layer disrupted developed fleece-rot. The fleece-rot lesions observed were more severe in sheep in the disrupted wetted treatments than in the intact wetted treatment. Interpretation of these differences was complicated by a possible reaction of the skin to the solvent used. The differences were not due to an effect of treatment on fleece wettability. No fleece-rot developed in the sheep not wetted and application of the solvent alone did not induce fleece-rot.

Animals↗
PubMed1981

Observations on fibre diameter variation of sheep in relation to fleece-rot and body strike susceptibility.

A comparative study of various fleece properties known to influence fleece-rot susceptibility was made in a merino flock consisting of sheep which were found to be either resistant or susceptible to fleece-rot and body strike following heavy rains. The fleece properties measured were fibre diameter, fibre diameter, fibre diameter variation, wax content, suint content, wax to suint ratio, suint pH, insoluble nitrogen content, wool colour and wettability. Fibre diameter variation, due mainly to the presence of coarse, secondary fibres in the staple, was the only fleece property which differed significantly (p less than 0.001) between resistant and susceptible animals. The coefficient of variation of fibre diameter was lowered from a mean value of 22.7 +/- 0.3% in susceptible sheep to 20.0 +/- 0.3% in resistant sheep. A causal relationship between high fibre diameter variation and fleece-rot susceptibility is suggested. Sheep with irregular fibre size may retain free moisture in the fleece for longer, and thereby become more susceptible to fleece-rot than sheep with uniform fibre diameter, other predisposing factors being equal.

Animals↗
PubMed1984

Behavior of amitraz in cattle dipping baths.

The settling rates of 0.025% w/v amitraz (used as a 50% w/w active ingredient wettable powder) and lime stabiliser (0.7% Ca(OH)2) were studied in cattle dipping baths in the Tick Quarantine Area of northern New South Wales. Although lime settled more rapidly than amitraz, the rate for both decreased as the number of cattle dipped increased. After a total of 1,200 head had been dipped the settling rate during the hour following stirring was negligible, and re-stirring was not necessary within the hour following use. Baths could also be cleaned of heavy sediment by scooping without significant loss of chemicals. When the bath volume was allowed to decrease to 2,100 liters below working volume no significant changes in amitraz and Ca(OH)2 concentrations occurred. Data collected from 796 baths showed a significant concentration change of +0.00066% amitraz and -0.017% Ca (OH)2 per 1,000 head of cattle. Replenishment per 700 liters of water with 254 g amitraz was found to be in good agreement with 250 g recommended by the manufacturer, while 12.53 kg for lime was substantially more than the 10 kg recommended.

Animal Husbandry↗
PubMed1989

The tensile strength of the union between various glass ionomer cements and various composite resins.

Increasing use is being made of the glass ionomer cements as a lining for composite resin restorations, particularly when restoring posterior teeth. It has been suggested that it is possible to obtain a mechanical union between the two materials by etching the surface of the cement. This paper discusses the result of testing a broad variety of combinations of different glass ionomer cements and composite resins that have been reported on previously, and suggests that a number of factors need to be taken into account if the optimum physical properties are to be achieved from the union. There would appear to be four main factors which dictate the final strength of the union. The tensile strength of the cement itself is of primary importance and it seems the wettability of the resin bonding agent is also significant. When using some of the less heavily filled composite resins, the stresses set up by the setting contraction of the resin may be too great and, finally, the more heavily filled composite resins for restoration of posterior teeth often prove difficult to adapt to the underlying cement. With careful clinical handling, the so-called 'sandwich' technique is very useful. However, not all combinations of glass ionomer cement and composite resin will unite with sufficient strength to be successful clinically.

Chemical Phenomena↗
PubMed1975

Improvement of solubility and dissolution rate of poorly water-soluble salicylic acid by a spray-drying technique.

Spray drying techniques have been applied to improve the solubility and dissolution rate of poorly water-soluble salicylic acid. Spray drying of the acid dispersed in acacia solutions resulted in as much as a 50% improvement in the solubility of the product. Solubility improvement was closely related not only to the concentration of acacia but also the amount of amorphous material in the spray-dried products. The heat of solution was inversely related to these parameters. The dissolution rate of spray-dried product was almost instantaneous being about 60 times faster than that of the original powder. A great improvement in the wettability of the spray-dried material seemed to be mainly responsible for the increase of dissolution rate.

Diffusion↗
PubMed1978

Bioavailability of griseofulvin from a novel capsule formulation.

The in vivo availability of griseofulvin from a novel formulation has been compared with the micronized powder. The formulation technique involves the conversion of the hydrophobic surface of the drug to a hydrophilic one by treatment with a film forming polymer. This enhances the wettability of the power, and increases its dissolution rate. The results of the in vivo study show the formulation technique has increased the rate and extent of bioavailability of griseofulvin when compared with the non-treated powder.

Biological Availability↗
PubMed1981

Analysis of factors affecting the mean sizes of granules produced from ternary mixtures of powders.

Multiple linear regression analysis has been used to relate the mean sizes of granules prepared from ternary mixtures of powders to such physical properties as particle size, solubility and wettability and to processing variables such as the amount of binder and the proportions of the different components. The major influences on granule size were the amount of binder and the affinity of the third component for the binder liquids.

Particle Size↗
PubMed1984

Controlled release of radioprotective agents from matrix tablets--effect of preparative conditions on release rates.

Release rates of radioprotective agents from insoluble matrix tablets were measured as a function of ethylcellulose/stearic acid ratio and active ingredient concentration in the matrix. The influence of the compacting pressure applied during tablet formation on the release of these aminothiol compounds was also examined. The kinetic data conformed with the Higuchi square root equation and first order release. As both plots were linearly acceptable, a statistical method for release mechanism identification using the kinetic experimental results obtained without any further transformation was used. This non-linear regression search procedure accompanied by the chi 2-square test has shown that that aminothiol release from the matrix tablets definitely follows the Higuchi square root equation. Increasing the ethylcellulose amount in the matrix consequently improves the degree of wettability and leads to a faster rate of solvent penetration. This tends to release the aminothiols more rapidly from the matrix tablets. Solvent penetration, which also follows a square root of time relationship, is probably the rate-limiting factor in the release process. The linear increase in release rates of the aminothiols observed with ethylcellulose concentration is explained by a parallel increase in the porosity of the matrix tablets. Increase in the drug concentration in the tablet increases the cysteine hydrochloride release rate and decreases the cysteamine hydrochloride release rate. A similar effect was also observed by applying increasing compacting pressure during matrix tablet formation. It was suggested that these two experimental factors differently affect the internal structure of the matrix during the preparation process.(ABSTRACT TRUNCATED AT 250 WORDS)

Cellulose↗
PubMed1986

Studies on metronidazole tablet formulations.

Incorporating polyvinylpyrrolidone, gelatin and methylcellulose binding agents in a metronidazole formulation alters the tensile strength, disintegration and dissolution times of the tablets by reducing their wettability as measured by the adhesion tension of water. Correlations have been established between the disintegration times, D and the dissolution times t50, t90 and t1 (derived from the equation of Noyes & Whitney). A correlation has also been established between the adhesion tension of water on the tablets and the disintegration and dissolution times. These correlations depend on the nature and concentration of binder used.

Adhesiveness↗
PubMed1989

Effects of tapioca obtained from cassava (Manihot utilissima) on the disintegration and dissolution rates of paracetamol tablets.

The properties of tapioca obtained from cassava (Manihot utilissima) have been evaluated. Its binding effect in tablets of paracetamol on the disintegration and dissolution rates was compared with tablets prepared with polyvinylpyrrolidone and gelatin. The nature and amount of the binders were found to alter the disintegration and dissolution rates of the tablets by reducing their wettability as measured by the adhesion tension of water. A linear relationship has been found to exist between the adhesion of water on the tablets and their disintegration and dissolution rates.

Acetaminophen↗
PubMed1990

Rapidly absorbed solid oral formulations of ibuprofen using water-soluble gelatin.

Rapidly absorbed oral dosage forms of ibuprofen using water-soluble gelatin (hydrolysate of common gelatin: mean mol. wt: 6000) have been studied and compared with tablets prepared with common gelatin (mean mol. wt: 100,000) and commercial tablets. Spray-dried and speed-kneaded powders, two types of granules and tablets were prepared with water-soluble gelatin. The in-vitro dissolution rates of water-soluble gelatin preparations were significantly faster than those of commercial tablets, whereas the tablets prepared using common gelatin had slower dissolution rates than commercial tablets. Water-soluble gelatin enhanced the dissolution rate of ibuprofen by improving the wettability of the drug particle surface by water, without any interaction in solution and the solid state. The absorption behaviour of various preparations was evaluated in four beagle dogs. The peak concentration time (tmax) of the water-soluble gelatin preparations was significantly shorter than that of tablets prepared with common gelatin and commercial tablets. The maximum concentration (cmax) and the area under the serum concentration-time curve (AUCo-10 h) were similar in all cases. The serum concentration profiles of water-soluble gelatin solid preparations were almost the same as those of the solutions. On the other hand, the profiles of the common gelatin tablets were similar to those of the commercial tablets. The mean absorption time (MAT) from water-soluble gelatin preparations was about 0.7 h, while the MAT from commercial tablets and common gelatin tablets was about 1.2 h. The differences in the MAT of water-soluble gelatin preparations and commercial tablets or common gelatin tablets were the same as the differences in mean dissolution time (MDT) in gastrointestinal fluid.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Improvement of absorption rate of indomethacin and reduction of stomach irritation by alginate dispersions.

The dissolution rates of indomethacin from low molecular weight (mol. wt) alginate dispersions were significantly enhanced in comparison with that of indomethacin alone. The dispersion with lower mol. wt alginate exhibited more rapid dissolution rate than that of dispersion with higher mol. wt alginate. These enhanced dissolution rates of indomethacin by alginate may be due to the improvement of wettability and the decrease of crystallinity and crystal size. The absorption rate from alginate dispersions was enhanced in comparison with that from indomethacin alone, and enhanced only the rate of bioavailability in beagle dogs and volunteers. In addition, indomethacin-induced gastric lesions were reduced by dispersing indomethacin in alginate.

Administration, Oral↗