Potential role for epidermal Langerhans cells in nicotinic acid-induced vasodilatation in the mouse.

OBJECTIVE: Our objective is to study the role of cutaneous Langerhans cells on a mouse model of nicotinic acid-induced vasodilatation. METHODS: Nicotinic acid-induced vasodilatation was studied in the mouse ear by laser Doppler flowmetry prior to and at intervals after Langerhans cells depletion by treatment with hydrocortisone. RESULTS: Nicotinic acid evoked a dose-dependent increase in perfusion in the mouse ear. Treatment with 1 % hydrocortisone resulted in substantial depletion of Langerhans cells, accompanied by failure to show vasodilatation in response to nicotinic acid. Partial recovery of Langerhans cells on day 53 post-treatment was associated with a partial vasodilatation response. To exclude non-specific effects of hydrocortisone on arachidonic acid metabolism, the ability of the mice to mount an edema response to phorbol 12-myristate 13-acetate was evaluated. On day 9 post hydrocortisone, phorbol 12-myristate 13-acetate failed to evoke an edema response. However, on day 22 post hydrocortisone, the edema response in the hydrocortisone-treated animals was indistinguishable from that of control animals. CONCLUSIONS: These results suggest that Langerhans cells are responsible for nicotinic acid-induced vasodilatation.

Analysis of rheological properties of bone cements.

The rheological properties of three commercially available bone cements, CMW 1, Palacos R and Cemex ISOPLASTIC, were investigated. Testing was undertaken at both 25 and 37 degrees C using an oscillating parallel plate rheometer. Results showed that the three high viscosity cements exhibited distinct differences in curing rate, with CMW 1 curing in 8.7 min, Palacos R and Cemex ISOPLASTIC in 13 min at 25 degrees C. Furthermore it was found that these curing rates were strongly temperature dependent, with curing rates being halved at 37 degrees C. By monitoring the change of viscosity with time over the entire curing process, the results showed that these cements had differing viscosity profiles and hence exhibit very different handling characteristics. However, all the cements reached the same maximum viscosity of 75 x 10(3) Pa s. Also, the change in elastic/viscous moduli and tan delta with time, show the cements changing from a viscous material to an elastic solid with a clear peak in the viscous modulus during the latter stages of curing. These results give valuable information about the changes in rheological properties for each commercial bone cement, especially during the final curing process.

A sensor to detect the early stages in the development of crystalline Proteus mirabilis biofilm on indwelling bladder catheters.

A simple sensor has been developed to detect the early stages of urinary catheter encrustation and avoid the clinical crises induced by catheter blockage. In laboratory models of colonization by Proteus mirabilis, the sensor signaled encrustation at an average time of 43 h before catheters were blocked with crystalline biofilm.

Reduced adherence of Candida to silane-treated silicone rubber.

Silicone rubber is widely used in the construction of medical devices that can provide an essential role in the treatment of human illness. However, subsequent microbial colonization of silicone rubber can result in clinical infection or device failure. The objective of this study was to determine the effectiveness of a novel silane-treated silicone rubber in inhibiting microbial adherence and material penetration. Test material was prepared by a combination of argon plasma discharge treatment and fluorinated silane coupling. Chemicophysical changes were then confirmed by X-ray photoelectron spectroscopy, contact-angle measurement, and atomic force microscopy. Two separate adherence assays and a material penetration assay assessed the performance of the new material against four strains of Candida species. Results showed a significant reduction (p < 0.01) of Candida albicans GDH 2346 adherence to silane-treated silicone compared with untreated controls. This reduction was still evident after the incorporation of saliva into the assay. Adherence inhibition also occurred with Candida tropicalis MMU and Candida krusei NCYC, although this was assay dependent. Reduced penetration of silane-treated silicone by Candida was evident when compared to untreated controls, plaster-processed silicone, and acrylic-processed silicone. To summarize, a novel silicone rubber material is described that inhibits both candidal adherence and material penetration. The clinical benefit and performance of this material remains to be determined.

Designing a prosthesis to simulate the elastic properties of skin.

The materials which are currently used to make maxillofacial prostheses are far from ideal and require considerable improvement with respect to their ability to mimic the properties of skin. To this aim, a novel three-layered maxillofacial prosthesis has been designed consisting of a silicone rubber base layer, an inner gel layer and an outer polymeric coating (to simulate the elastic properties of skin). The aim of the work in this study was to develop the inner silicone gel layer which displays similar properties to facial skin. Through the use of unique linear extensometry testing, in vivo measurements for the Area under the Curve (AUC), Hysteresis (viscoelastic behaviour), Fmax (maximum force), F30 and F60 (force after 30 and 60 seconds) were obtained from the facial skin of 15 volunteers. The results were used as a basis for developing silicone gel formulations for the inner layer, to closely resemble those of facial skin. Gels were made by the addition of both low and high molecular weight unreactive silicone fluids and were further tested for compression, water absorption and dehydration. Testing showed that a gel has been produced that closely simulates the elastic properties of skin when bonded to a base silicone rubber layer. Further testing will need to deduce whether these properties will be affected by the addition of the outer polymeric layer.

Surface modification of an experimental silicone rubber aimed at reducing initial candidal adhesion.

Silicone rubber, which is a widely used biomaterial, is often used to make soft liners for permanent denture. Colonization of denture soft lining materials by Candida albicans can result in clinical problems. The aim of this study was to chemically modify the surface of an experimental silicone rubber in order to produce a silicone that was less susceptible to candidal colonization. Surface modification was carried out with the use of argon-plasma bombardment followed by silane treatment, which caused the incorporation of either hydrophilic or hydrophobic functional groups onto the surface. Changes in water contact angles and chemical analysis of the materials with scanning ion mass spectroscopy confirmed surface changes. In vitro assays were carried out using C. albicans to measure levels of adherence to the surface-modified silicone after 1 h. C. albicans exhibited very low adherence to all silane-treated surfaces, whether hydrophobic or hydrophilic. This led to the conclusion that incorporated long-chain functional groups were inhibiting the adherence of the yeast, possibly by the formation of a barrier between the surface of the material and the yeast. In conclusion, silane surface treatment of an experimental silicone rubber has been successful in reducing candidal adherence.

Golgi-to-endoplasmic reticulum (ER) retrograde traffic in yeast requires Dsl1p, a component of the ER target site that interacts with a COPI coat subunit.

DSL1 was identified through its genetic interaction with SLY1, which encodes a t-SNARE-interacting protein that functions in endoplasmic reticulum (ER)-to-Golgi traffic. Conditional dsl1 mutants exhibit a block in ER-to-Golgi traffic at the restrictive temperature. Here, we show that dsl1 mutants are defective for retrograde Golgi-to-ER traffic, even under conditions where no anterograde transport block is evident. These results suggest that the primary function of Dsl1p may be in retrograde traffic, and that retrograde defects can lead to secondary defects in anterograde traffic. Dsl1p is an ER-localized peripheral membrane protein that can be extracted from the membrane in a multiprotein complex. Immunoisolation of the complex yielded Dsl1p and proteins of approximately 80 and approximately 55 kDa. The approximately 80-kDa protein has been identified as Tip20p, a protein that others have shown to exist in a tight complex with Sec20p, which is approximately 50 kDa. Both Sec20p and Tip20p function in retrograde Golgi-to-ER traffic, are ER-localized, and bind to the ER t-SNARE Ufe1p. These findings suggest that an ER-localized complex of Dsl1p, Sec20p, and Tip20p functions in retrograde traffic, perhaps upstream of a Sly1p/Ufe1p complex. Last, we show that Dsl1p interacts with the delta-subunit of the retrograde COPI coat, Ret2p, and discuss possible roles for this interaction.

The effect of disinfection and a wetting agent on the wettability of addition-polymerized silicone impression materials.

STATEMENT OF PROBLEM: The wettability of silicone impression materials is poor, which may lead to voids within casts. All impression materials should be disinfected before use, but disinfection may affect their wettability. PURPOSE: This study evaluated the effect of disinfection procedures and the use of a surface wetting agent on the wettability of 4 addition-polymerized silicone impression materials. MATERIAL AND METHODS: Testing specimens were made from 4 addition silicone materials (light-bodied President, light-bodied Extrude, medium-bodied Extrude, and Aquasil). Two disinfection solutions (Actichlor and Perform) and 1 wetting agent (Vacufilm) were used. The test conditions were as follows: (A) dry, (B) Vacufilm, (C) Actichlor (10-minute soak), (D) Actichlor (10-minute soak) and Vacufilm, (E) Perform (10 minute-soak), and (F) Perform (10-minute soak) and Vacufilm. A dynamic contact angle analyzer was used to measure the wettability of specimens. Mean results were compared with 1-way ANOVA, and multiple comparisons were made with the Bonferroni method. RESULTS: Treatments C, D, and F had no significant effect on the wettability of the materials. Treatment B significantly reduced the contact angle for light-bodied President (P< .01) and Aquasil (P< .05). Treatment E significantly increased the contact angle for light- and medium-bodied Extrude and Aquasil (P< .001). CONCLUSION: Disinfection with Actichlor is recommended in preference to Perform to maintain the wettability of impression materials. Treatment with Vacufilm after disinfection is recommended to improve the wettability of materials and thus reduce the likelihood of voids within casts.

Wettability of visible light-curing denture lining materials.

PURPOSE: Wetting characteristics of denture lining materials indicate the degree of salivary lubricating effect, which promotes denture retention and patient comfort. This in vitro study investigated the wettability of ten commercially available visible light-cured denture lining materials. MATERIALS AND METHODS: Ten soft and hard visible light-curing materials, one autopolymerized hard lining material, and one autopolymerized denture base material were evaluated for wettability. Wettability was estimated by measuring the equilibrium and hysteresis contact angles using the dynamic contact angle analysis, or Wilhelmy, technique. RESULTS: The equilibrium contact angle ranged from 59.9 to 77.3 degrees, and contact angle hysteresis ranged from 14.7 to 30.6 degrees. CONCLUSION: Visible light-curing lining materials exhibit wetting properties similar to the conventional hard lining and denture base materials.

Wettability of denture materials.

OBJECTIVE: To promote denture retention and denture comfort, denture materials should possess adequate wettability. This in vitro study investigated the wettability of nine commercially available dental materials. METHOD AND MATERIALS: Four denture base materials, two denture hard lining materials, and three denture soft lining materials (with and without varnish treatment) were tested. The wettability measurements were made using the dynamic contact angle analysis technique. The equilibrium and hysteresis angles obtained were used for the comparisons. RESULTS: The equilibrium contact angle (thetae) ranged from 63.9 (Permaflex + varnish) to 81.0 degrees (Mollosil + varnish). The differences observed among the materials tested were statistically significant. The contact angle hysteresis ranged from 16.0 (SR 3/60 Triplex) to 51.2 degrees (Mollosil), and there was a statistically significant difference among the materials. CONCLUSION: The heat-polymerized soft lining materials exhibited the greatest equilibrium contact angle, the autopolymerized soft liner had the lowest value, and the denture base materials had intermediate values. The soft liners showed greater contact angle hysteresis than all other materials. The use of varnish altered the wetting characteristics.

Dsl1p, an essential protein required for membrane traffic at the endoplasmic reticulum/Golgi interface in yeast.

To identify novel factors required for ER to Golgi transport in yeast we performed a screen for genes that, when mutated, confer a dependence on a dominant mutant form of the ER to Golgi vesicle docking factor Sly1p, termed Sly1-20p. DSL1, a novel gene isolated in the screen, encodes an essential protein with a predicted molecular mass of 88 kDa. DSL1 is required for transport between the ER and the Golgi because strains bearing mutant alleles of this gene accumulate the pre-Golgi form of transported proteins at the restrictive temperature. Two strains bearing temperature-sensitive alleles of DSL1 display distinct phenotypes as observed by electron microscopy at the restrictive temperature; although both strains accumulate ER membrane, one also accumulates vesicles. Interestingly, the inviability of strains bearing several mutant alleles of DSL1 can be suppressed by expression of either Erv14p (a protein required for the movement of a specific protein from the ER to the Golgi), Sec21p (the gamma-subunit of the COPI coat protein complex coatomer), or Sly1-20p. Because the strongest suppressor is SEC21, we proposed that Dsl1p functions primarily in retrograde Golgi to ER traffic, although it is possible that Dsl1p functions in anterograde traffic as well, perhaps at the docking stage, as suggested by the suppression by SLY1-20.

Phosphorylation of the vesicle-tethering protein p115 by a casein kinase II-like enzyme is required for Golgi reassembly from isolated mitotic fragments.

Coat protein I (COPI) transport vesicles can be tethered to Golgi membranes by a complex of fibrous, coiled-coil proteins comprising p115, Giantin and GM130. p115 has been postulated to act as a bridge, linking Giantin on the vesicle to GM130 on the Golgi membrane. Here we show that the acidic COOH terminus of p115 mediates binding to both GM130 and Giantin as well as linking the two together. Phosphorylation of serine 941 within this acidic domain enhances the binding as well as the link between them. Phosphorylation is mediated by casein kinase II (CKII) or a CKII-like kinase. Surprisingly, the highly conserved NH(2)-terminal head domain of p115 is not required for the NSF (N-ethylmaleimide-sensitive fusion protein)-catalyzed reassembly of cisternae from mitotic Golgi fragments in a cell-free system. However, the ability of p115 to link GM130 to Giantin and the phosphorylation of p115 at serine 941 are required for NSF-catalyzed cisternal regrowth. p115 phosphorylation may be required for the transition from COPI vesicle tethering to COPI vesicle docking, an event that involves the formation of trans-SNARE [corrected] (trans-soluble NSF attachment protein [SNAP] receptor) complexes.

Cell biology. ER-to-Golgi traffic--this bud's for you.

How do protein-transporting vesicles, which bud from the endoplasmic reticulum (ER), specifically dock to, and fuse with, the Golgi apparatus? In their Perspective, Brittle and Waters discuss new work (Allan et al.) suggesting that some vesicle-associated docking and fusion proteins are "programmed" during vesicle budding from the ER and direct downstream events that occur during fusion of these transport vesicles with the membranes of the Golgi.

Interstitial cystitis: a retrospective analysis of treatment with pentosan polysulfate and follow-up patient survey.

To evaluate the efficacy and safety of pentosan polysulfate sodium (PPS) in relieving symptoms of interstitial cystitis, the authors retrospectively reviewed charts of 260 patients in whom interstitial cystitis had been diagnosed. Subsequently, they conducted a follow-up phone interview or mail survey of those patients who were treated with PPS to investigate changes in the patients' symptoms, adverse effects, and change in quality of life. The control group consisted of patients whose interstitial cystitis had been diagnosed at cystoscopy and had a duration of at least 1 year and who had taken at least one or more oral medications for their symptoms. The average length of treatment was 9.3 months among the 27 subjects on PPS therapy. The mean length of time that they had diagnosed interstitial cystitis was 35.63 months and 48.78 months for the PPS-treated and control groups, respectively, with no statistically significant difference. Changes in frequency, urgency, and pain were greater in the treatment group and statistically significant (P = .11, P = .49, and P = .004, respectively). No change occurred in the rate of nocturia in the PPS-treated group compared with that in the control group. Symptoms of both groups improved over time, but improvement was statistically significantly greater in the treatment group (P = .001) over the treatment interval. The most common side effect attributable to PPS was diarrhea in 15% of subjects. Pentosan proved to be an efficacious option for reducing the debilitating symptoms of interstitial cystitis.

Membrane tethering and fusion in the secretory and endocytic pathways.

Studies of intracellular trafficking over the past decade or so have led to striking advances in our understanding of the molecular processes by which transport intermediates dock and fuse. SNARE proteins play a central role, assembling into complexes that bridge membranes and may catalyze membrane fusion directly. In general, different SNARE proteins operate in different intracellular trafficking pathways, so recent reports that SNARE assembly in vitro is promiscuous have come as something of a surprise. We propose a model in which proper SNARE assembly is under kinetic control, orchestrated by members of the Sec1 protein family, small GTP-binding Rab proteins, and a diverse assortment of tethering proteins.

Sec34p, a protein required for vesicle tethering to the yeast Golgi apparatus, is in a complex with Sec35p.

A screen for mutants of Saccharomyces cerevisiae secretory pathway components previously yielded sec34, a mutant that accumulates numerous vesicles and fails to transport proteins from the ER to the Golgi complex at the restrictive temperature (Wuestehube, L.J., R. Duden, A. Eun, S. Hamamoto, P. Korn, R. Ram, and R. Schekman. 1996. Genetics. 142:393-406). We find that SEC34 encodes a novel protein of 93-kD, peripherally associated with membranes. The temperature-sensitive phenotype of sec34-2 is suppressed by the rab GTPase Ypt1p that functions early in the secretory pathway, or by the dominant form of the ER to Golgi complex target-SNARE (soluble N-ethylmaleimide sensitive fusion protein attachment protein receptor)-associated protein Sly1p, Sly1-20p. Weaker suppression is evident upon overexpression of genes encoding the vesicle tethering factor Uso1p or the vesicle-SNAREs Sec22p, Bet1p, or Ykt6p. This genetic suppression profile is similar to that of sec35-1, a mutant allele of a gene encoding an ER to Golgi vesicle tethering factor and, like Sec35p, Sec34p is required in vitro for vesicle tethering. sec34-2 and sec35-1 display a synthetic lethal interaction, a genetic result explained by the finding that Sec34p and Sec35p can interact by two-hybrid analysis. Fractionation of yeast cytosol indicates that Sec34p and Sec35p exist in an approximately 750-kD protein complex. Finally, we describe RUD3, a novel gene identified through a genetic screen for multicopy suppressors of a mutation in USO1, which suppresses the sec34-2 mutation as well.

Membrane tethering in intracellular transport.

Studies of various membrane trafficking steps over the past year indicate that membranes are tethered together prior to the interaction of v-SNAREs and t-SNAREs across the membrane junction. The tethering proteins identified to date are quite large, being either fibrous proteins or multimeric protein complexes. The tethering factors employed at different steps are evolutionarily unrelated, yet their function seems to be closely tied to the more highly conserved Rab GTPases. Tethering factors may collaborate with Rabs and SNAREs to generate targeting specificity in the secretory pathway.

Wettability of silicone rubber maxillofacial prosthetic materials.

STATEMENT OF PROBLEM: Maxillofacial prosthetic materials that contact skin or mucosa should have good wettability. A material that is easily wetted will form a superior lubricating layer between the supporting tissues and, thus, reduce friction and patient discomfort. The surface energy of a maxillofacial prosthetic material will give an indication of the amount of energy available for adhesion and of the susceptibility of the material to bacterial adhesion. PURPOSE: This study evaluated the wettability and surface energies of a range of commercially available silicone rubber maxillofacial prosthetic materials. MATERIAL AND METHODS: Contact angles and surface energies were measured by using a dynamic contact angle measuring technique. Four commonly used silicone maxillofacial materials were tested and their properties compared with those of an acrylic resin denture base material and a widely used denture soft lining material. RESULTS: There were no significant differences in the wettability of the silicone rubber materials. All materials were significantly less wetted than the denture acrylic resin material. There were no significant differences in the surface energies of the silicone rubber materials, but all were significantly lower than denture acrylic resin material. CONCLUSIONS: The Cahn dynamic contact angle analyzer was a quick and reproducible method for determining the contact angles and surface energies of maxillofacial materials. Further work is needed to improve the wettability of silicone rubber materials used for maxillofacial prostheses, thus, reducing their potential to produce friction with tissues.

Mechanical properties of an experimental denture soft lining material.

OBJECTIVES: The objective of the present study was to evaluate the mechanical properties of an experimental formulation (Exp. 1) in order to assess its potential as a denture soft lining material. The same properties of a popular commercially available denture soft lining material (Molloplast-B) were determined and compared with the properties of Exp. 1. METHODS: Exp. 1 specimens were obtained by curing for 24 h at room temperature after the addition of the appropriate amounts of catalyst and cross-linker. Molloplast-B specimens were obtained after curing according to the manufacturer's instructions. The properties measured in the study were hardness, tear resistance, tensile strength and the bond strength of the material to a heat-cured acrylic denture base material. RESULTS: Exp. 1 had a significantly greater tensile strength, percent elongation, tear resistance and peel strength (p < 0.0001) than Molloplast-B. There was no significant difference in the hardness values of the two materials, although Molloplast-B had a significantly higher tensile bond and shear bond strength (p < 0.05). CONCLUSIONS: It was concluded that there was no significant difference in the hardness of Exp. 1 and Molloplast-B. Exp. 1 had superior tensile and tear properties. Its peel bond strength was superior to that of Molloplast-B, although its tensile bond strength and shear bond strength were less.

Purification and characterization of a novel 13 S hetero-oligomeric protein complex that stimulates in vitro Golgi transport.

Intracellular protein traffic involves a tightly regulated series of events in which a membrane-bounded vesicles bud from one compartment and are specifically targeted to the next compartment, where they dock and fuse. A cell-free system that reconstitutes vesicle trafficking between the cis and medial Golgi cisternae has been used previously to identify several proteins involved in vesicular transport (N-ethylmaleimide-sensitive fusion protein, soluble N-ethylmaleimide-sensitive fusion protein attachment proteins, p115, and p16); however, these factors are insufficient to drive the transport reaction. We have used a modified version of this in vitro intra-Golgi transport assay to guide purification of a new transport-stimulating activity. The active component is a 13 S hetero-oligomeric complex consisting of at least five polypeptides (approximately 110, 109, 90, 82, and 71 kDa), which we term Golgi transport complex (GTC). Hydrodynamic properties suggest that GTC is approximately 800 kDa and nonglobular. We obtained peptide sequence information from the 90-kDa subunit (GTC-90) that allowed us to identify a number of GTC-90 cDNAs. Comparison of these cDNAs with one another and with the genomic sequence suggests that the GTC-90 mRNA is alternatively spliced. Anti-GTC-90 antibodies inhibit the in vitro Golgi transport assay, confirming the functionality of the purified complex. Subcellular fractionation indicates that GTC-90 exists in both membrane and cytosolic pools, with the cytosolic pool associated exclusively with the GTC complex. The membrane-associated pool of GTC-90 is localized to the Golgi apparatus.