The Cyanelles (Organelles of a Low Evolutionary Scale) Possess a Phosphate-Translocator and a Glucose-Carrier in Cyanophora paradoxa

Cyanelles from Cyanophora paradoxa can easily be isolated and assayed for their carrier composition by the silicone oil filtering technique. The present investigation demonstrates a P_i-translocator transferring phosphate, dihydroxyacetone phosphate and 3-phosphoglycerate in a counter exchange mode in cyanelles as in chloroplasts of higher plants. The uptake of P_i is inhibited by dihydroxyacetone phosphate, phosphoglycerate and glucose-6-P, only poorly by phosphoenolpyruvate and not by 2-phosphoglycerate. The inhibitors pyridoxalphosphate and 4,4′diisothiocyanostilbene-2,2K'disulfonic acid at low concentration also affect P_i-uptake. Cyanelles probably transport photosynthate (reductant and ATP) by triosephosphates. This is the first demonstration of a phosphate translocator in an organism of a low evolutionary scale. Cyanelles also transport glucose which proceeds in two phases. In the lower concentration range (≤ 2.5 mM), glucose penetrates by facilitated diffusion, whereas transport follows first-order kinetics at higher amounts (> 2.5 mM). In the low concentration range, glucose-transport is affected by high concentrations of 3-O-methylglucose and fructose. The physiological role of the glucose-transport carrier in Cyanophora is doubtful. It may function in transporting glucose into cyanelles if the carbon level inside them becomes limiting, e.g. in dark periods.     

Caffeinated soft drinks reduce bacterial prevalence in voice prosthetic biofilms

Laryngectomized patients use indwelling silicone rubber voice prostheses, placed in a surgically created fistula in between the trachea and the esophagus, for voice and speech rehabilitation. At the esophageal side, these voice prostheses rapidly become colonized by a thick biofilm consisting of a variety of oral and skin bacteria and yeasts, and on average, after 3–4 months a prosthesis has to be replaced. In this study, the influence of caffeinated soft drinks on biofilm formation on silicone rubber voice prostheses has been investigated in a modified Robbins device. Robbins devices were first inoculated with the total cultivable microflora from an explanted voice prosthesis for 3 d, after which the devices were perfused three times daily over a 12 day period with 650 ml of either phosphate buffered saline or carbonated mineral water (controls), caffeinated soft drinks (two types), or a decaffeinated and a sugar‐free version of one of the caffeinated soft drinks. At the end of a day, during the experimental period, the devices were filled with growth medium for 30 min. Both caffeinated soft drinks reduced bacterial prevalence in the biofilms to 1–5% of the control, while yeasts thrived in voice prosthetic biofilms exposed to caffeinated soft drinks. Neither the controls, nor the decaffeinated soft drink, nor the sugar‐free version of this showed these effects on bacterial prevalence.     

Adhesion and motility of fouling diatoms on a silicone elastomer

Recent demands for non-toxic antifouling technologies have led to increased interest in coatings based on silicone elastomers that ‘release’ macrofouling organisms when hydrodynamic conditions are sufficiently robust. However, these types of coatings accumulate diatom slimes, which are not released even from vessels operating at high speeds ( > 30 knots). In this study, adhesion strength and motility of three common fouling diatoms (Amphora coffeaeformis var. perpusilla (Grunow) Cleve, Craspedostauros australis Cox and Navicula perminuta Grunow) were measured on a polydimethylsiloxane elastomer (PDMSE) and acid-washed glass. Adhesion of the three species was stronger to PDMSE than to glass but the adhesion strengths varied. The wall shear stress required to remove 50% of cells from PDMSE was 17 Pa for Craspedostauros, 24 Pa for Amphora and >> 53 Pa for Navicula; the corresponding values for glass were 3, 10 and 25 Pa. In contrast, the motility of the three species showed little or no correlation between the two surfaces. Craspedostauros moved equally well on glass and PDMSE, Amphora moved more on glass initially before movement ceased and Navicula moved more on PDMSE before movement ceased. The results show that fouling diatoms adhere more strongly to a hydrophobic PDMSE surface, and this feature may contribute to their successful colonization of low surface energy, foul-release coatings. The results also indicate that diatom motility is not related to adhesion strength, and motility does not appear to be a useful indicator of surface preference by diatoms.     

Enhanced adhesion and chemoattraction of zoospores of the fouling alga enteromorpha to some foul‐release silicone elastomers

Significantly higher numbers of zoospores of the fouling, green alga Enteromorpha adhered to silicone elastomers cured by dibutyltin dilaurate (DBTDL) than to identical polymers cured by dibutyltin diacetate (DBTDA). Enhanced zoospore adhesion was shown to be due to the presence of DBTDL and the effect was concentration‐dependent. Further experiments revealed that enhanced zoospore adhesion also occurred to glass coverslips coated with lauric acid (C₁₂) and other saturated fatty acids. The possibility that fatty acids may act as chemical cues (chemoattractants), guiding motile zoospores to the substratum for settlement in the natural environment is discussed. Settlement of other fouling organisms to DBTDL‐cured silicone elastomers is currently being investigated.     

The Effects of Silicone Fluid Additives and Silicone Elastomer Matrices on Barnacle Adhesion Strength

Barnacle adhesion strength was used to screen seventy-seven polydimethylsiloxane elastomeric coatings for fouling-release properties. The test coatings were designed to investigate the effect on barnacle adhesion strength of silicone fluid additive type, additive location, additive molecular weight, additive loading level, mixtures of additives, coating matrix type and coating fillers. The type of silicone fluid additive was the primary controlling factor in barnacle fouling-release. The type of silicone matrix in which the fluid resided was found to alter the effect on fouling-release. Two PDMS fluids, DMSC15 and DBE224, significantly reduced the adhesion strength of barnacles compared to unmodified elastomers. Optimum fouling-release performance was dependent on the interaction of fluid type and elastomeric matrix.     

Adhesive interactions between voice prosthetic yeast and bacteria on silicone rubber in the absence and presence of saliva

Biofilms on silicone rubber voice prostheses are the major cause for frequent failure and replacement of these devices. The presence of both bacterial strains and yeast has been suggested to be crucial for the development of voice prosthetic biofilms. Adhesive interactions between Candida albicans, Candida krusei, and Candida tropicalis with 14 bacterial strains, all isolated from explanted voice prostheses were investigated in a parallel plate flow chamber. Bacteria were first allowed to adhere to silicone rubber, after which the flow chamber was perfused with yeast, suspended either in saliva or buffer. Generally, when yeast were adhering from buffer and saliva, the presence of adhering bacteria suppressed adhesion of yeast. In saliva, Rothia dentocariosa and Staphylococcus aureus enhanced adhesion of yeast, especially of C. albicans. This study shows that bacterial adhesion mostly reduces subsequent adhesion of yeast, while only a few bacterial strains stimulate adhesion of yeast, provided salivary adhesion mediators are present. Interestingly, different clinical studies have identified R. dentocariosa and S. aureus in biofilms on explanted prostheses of patients needing most frequent replacement, while C. albicans is one of the yeast generally held responsible for silicone rubber deterioration.     

Elevated serum silicon levels in women with silicone gel breast implants

The metatolic fate of silicone gel leaked from an intact or ruptured prosthesis is unknown. In this study, serum was blindly assayed by inductively coupled plasma atomic emission spectroscopy (ICP-AES) for elemental silicon in 72 women with silicone gel breast implants and 55 control women (mean age 48 yr, both groups). Blood was drawn and processed using silicon-free materials. The mean silicon level in controls was 0.13±0.07 mg/L (range 0.06–0.35 mg/L), whereas in implant patients, the mean was significantly higher at 0.28±0.22 mg/L (range 0.06–0.87 mg/L) (P<0.01, Student'st-test with correction for unequal variances). Using the mean of the control group +2 SD as a cutoff for normal range (0.27 mg/L), 25/72 (34.7%) implant patients exceeded this value, compared with 2/55 (3.6%) controls. There was no significant correlation between past rupture of one or both implants, current rupture at the time of the blood draw, or the number of years with implants and silicon levels. The results suggest that serum silicon levels are elevated in many women with silicone gel breast implants. The chemical species involved and kinetics of this elevation remain to be determined.     

Improved paclitaxel production in a two-phase suspension culture ofTaxus cuspidata using silicone cubes

Two-phase cultures ofTaxus cuspidata were performed using silicone cubes as a second phase in shake flasks for paclitaxel production. Among various taxanes, paclitaxel was selectively adsorbed on the silicon cubes. When silicone cubes were added to suspension culture ofTaxus cuspidata, paclitaxel production increased about 45 folds. The maximum paclitaxel production was 3.95 mg/L when 10% of silicone cubes were added to the culture at the 7th day from inoculation.     

Comparative studies on the interaction of proteins with a polydimethylsiloxane elastomer. II. The comparative antigenicity of primary and secondarily adsorbed IgG1 and IgG2a and their non-adsorbed counterparts

The antigenicity of bovine IgG1 and IgG2a adsorbed on a polydimethysiloxane (PEP) elastomer, on a widely used polystyrene (Imm 2, Dynatech) or immobilized as biotinylated proteins to streptavidin covalently bound to polystyrene (SA-PS) was compared using various monoclonal (mAbs) and polyclonal antibodies (pAb) to bovine IgG. The IgGs were either adsorbed as native proteins or pre-denatured with 6M Guanidine-HCl (Gu-HCl) or 6 M Gu-HCl/0.1% 2-mercaptoethanol. In special situations, bovine and human IgG was immobilized by secondary adsorption to an albumin monolayer adsorbed on either PEP or Imm 2. Results indicate that pre-denaturation of IgGs with 6 M Gu-HCl/2-mercaptoethanol destroys all antigenicity whereas those IgGs pretreated with 6 M-GuHCl are indistinguishable in their antigenicity from the IgGs adsorbed to either PEP or Imm 2 without such treatment. When immobilized on SA-PS, Gu-HCl-treated IgGs were significantly less detectable, especially when tested using mAbs. In general, IgGs adsorbed on PEP or Imm 2 were less antigenic than when immobilized on SA-PS. However, two monoclonals specific for the IgG2a(A2) allotypic variant, favored the adsorbed protein and one polyclonal best recognized the IgG2a(A1) variant adsorbed on Imm 2 rather than when adsorbed on PEP or immobilized on SA-PS. Both IgG1 and IgG2a, bound by apparent protein-protein interactions to an albumin monolayer, were significantly more detectable than when directly adsorbed on either Imm 2 or PEP. Using ¹²⁵l-antibody or its Fab fragment to reduce steric hindrance in detection, we observed the same differences in detectability as when measured by enzyme-linked immunosorbent assay. Failure to identify a steric hindrance effect and the preference of some antibodies for adsorbed allotypic variants, support the concept of adsorption-induced conformational change (AICC). We conclude that proteins adsorbed as a monolayer on the PEP elastomer used to form the envelope of silicone breast implants are conformationally altered, but not necessarily to the same extent or the same manner as when adsorbed on polystyrene. The significantly great antigenicity of secondarily adsorbed IgG suggests that it may be present in near native conformation. © 1997 John Wiley & Sons, Ltd.