Water, treated as the continuous liquid in and around cells.

In the quantitative treatment of non-covalent inter- and intra-cellular interactions taking place in water, in vitro as well as in vivo, it is essential to treat the surrounding and pervading liquid medium as the continuous medium. In the close vicinity of inter- and intra-cellular surfaces and of biopolymers the various different non-covalent forces may locally alter the structure of water in a number of ways, but these local structural changes can be quantitatively taken into account. The operative forces are: Lifshitz-van der Waals (LW) forces. Lewis acid-base (AB) forces and electrostatic (EL) forces. Of these, the AB forces are generally the preponderant ones, in aqueous media. This is due, inter alia, to the strong cohesive and adhesive hydrogen-bonding interactions typically occurring in and by water. Among the strong AB interactions occurring in water are hydrophobic attraction (the hydrophobic effect) and hydrophilic repulsion (hydration pressure). Also treated is the function of LW, AB and EL forces in: hydration; in the stability of particle and cell suspensions, the solubility of biopolymers, small organic solutes, and electrolytes; and in specific ligand-receptor (such as antigen-antibody) interactions.

Adsorption of biosurfactant on solid surfaces and consequences regarding the bioadhesion of Listeria monocytogenes LO28.

AIMS: The influence of biosurfactant compounds produced by a strain of Pseudomonas fluorescens on the adhesion of Listeria monocytogenes LO28 to polytetrafluoroethylene (PTFE) and AISI 304 stainless steel surfaces was investigated. METHODS AND RESULTS: The biosurfactant was produced according to a simple, novel technique based on cultivation on nutrient agar. Adhesion studies were performed using L. monocytogenes cells cultured at 20 or 37 degrees C. CONCLUSIONS: A substrate-dependent behaviour of the LO28 strain (larger number of cells adhering to stainless steel than to PTFE), and a significant reduction (< 90%) in microbial adhesion levels through the prior adsorption of biosurfactants on stainless steel surfaces, which can be related to a change in the electron-donor characteristics of this substratum, was demonstrated. SIGNIFICANCE AND IMPACT OF THE STUDY: The prior adsorption of biosurfactants on solid surfaces may constitute a new and effective means of combating the implantation of pathogenic micro-organisms in food processing plants.

Mechanisms of adjuvancy: I--Metal oxides as adjuvants.

The exact mechanism of how immune adjuvants function still remains largely unknown, despite their long history of use. This work reports the properties of alum and the related compounds Al(OH)3 or Al2O3. Experiments were performed in rats to determine the relative adjuvancy of silica, talc, ground glass, Al2O3, SnO2, ZrO2, hematite and magnetite. Antibody response and cell-mediated immunity (CMI) to ovalbumin (OVA) were determined and were found to be significantly enhanced by silica and talc. Antibody response to OVA was moderately enhanced by Al2O3, hematite, and magnetite, while CMI to OVA was not affected, SnO2, ZrO2, and ground glass only gave a slight adjuvant effect. The magnitude of adjuvancy appeared to correlate with the magnitude of the inflammatory response produced by each metal oxide and also correlated with their surface area. No correlation could be drawn between the hydrophilicity or hydrophobicity of the metal oxides and the magnitude of their adjuvancy.

Adjuvancy effect of different types of silicone gel.

Women with silicone gel-filled breast implants (SBIs) are likely to be at a slightly higher risk of developing an autoimmune-like syndrome. This risk, although small, may be associated with the immunological adjuvancy property of the silicone gel. However, not all silicone gels are chemically formulated exactly the same and their adjuvancy behavior may vary. This study compared, in rats, the adjuvant effect of three different lots of silicone gel using ovalbumin (OVA) as the test antigen. Test bleeds were taken at 21, 48, 62, and 84 days post immunization and the rat sera were analyzed for anti-OVA antibodies by enzyme linked immunosorbent assay (ELISA). A delayed type hypersensitivity (DTH) test was performed on all the treated rats beginning at 14 post-immunization days. The results showed that silicone gel #3 (McGhan lot #S0400488) produced the highest mean anti-OVA antibody titer followed by silicone gel #1 (DC lot #HH019581) and silicone gel #2 (McGhan lot #DP9339). The DTH results showed that rats treated with silicone gel #1 and #3 had a clear positive response, whereas silicone gel #2 caused only a minimal response. These results demonstrate the immunological adjuvancy difference among three types of silicone gel. The chemical composition of each of these silicone gels, that would help explain these results, is yet to be determined.

Kinetics and energetics of specific intermolecular interactions.

Taking into account the energy vs. distance functions of the aspecific (macroscopic) repulsion that usually prevails between antigen (Ag) and antibody (Ab) molecules in polar media, as well as the specific (microscopic) attraction between epitope and paratope of Ag and Ab, it proved possible to determine the kinetic constants (von Smoluchowski, 1917; Hammes, 1978) of Ag-Ab interactions, from the surface properties of Ag, Ab and the aqueous medium. The kinetic constants thus found correlate well with experimentally determined kinetic constants in comparable systems, and confirm the importance of the influence of the concentration of one of the reagents (e.g. the Ab) on the kinetic association constant (Van Regenmortel et al., 1994), which is largely due to steric hindrance. Applying the same energy vs. distance approach to the influence of temperature (T) on Ag-Ab reactions, it ensues that the familiar occurrence of an apparent 'enthalpy-entropy compensation' in aqueous media is in fact the relatively gratuitous outcome of a complex set of effects caused by an increase in T, on the total free energy, the hydration energy and, as a result, on the inter-epitope-paratope distance. A close correlation exists between the outcome of these surface-thermodynamic analyses and experimental results.

Induction of type II collagen arthritis in the DA rat using silicone gel as adjuvant.

The Dark Agouti (DA) rat has been shown recently to have a high susceptibility for developing arthritis when challenged with either heterologous or homologous collagen II mixed with mineral oil, or with mineral oil challenge alone. This study determined the arthritogenic potential of silicone gel by either mixing it with bovine collagen II (BII) or by injecting silicone gel alone in DA rats. The incidence of collagen induced arthritis was as follows: PBS group- 0/10, silicone gel group- 4/10, and IFA group- 8/9. Anti-BII antibodies were formed in most of the rats treated with either silicone gel or IFA and these groups of rats showed a positive DTH reaction. The PBS treated rats were negative for both anti-BII antibodies and DTH reaction. The incidence of arthritis formation in rats injected with silicone gel alone was 0/10, while the IFA injected rats showed an incidence of 8/10. Silicone gel taken from a commercial breast implant thus is capable of mediating collagen induced arthritis in the DA rat. However, silicone gel alone does not appear to be arthritogenic.

Induction of type II collagen arthritis in the DA rat using silicone gels and oils as adjuvant.

The relative safety (or otherwise) of silicone gel filled breast implants remains a controversial issue. The Dark Agouti (DA) rat has been shown recently to have a high susceptibility for developing arthritis. This study determined the arthritogenic potential of silicone gel, silicone oil, and the low molecular weight octamethylcyclotetrasiloxane (D4), by either mixing it with bovine collagen II (BII) or by injecting silicone gel alone in DA rats. Three separate experiments were performed using 110 female DA rats with 10 rats per treatment group. The incidence of collagen induced arthritis was as follows: Experiment I (6 micrograms BII)- PBS = 0/10, silicone gel = 4/10, and IFA = 8/9; Experiment II (125 micrograms BII)- PBS = 0/10, silicone gel = 7/10, IFA = 10/10, 1,000 cs silicone oil = 3/10, D4 = 0/10, and 1% D4 in 1,000 cs silicone oil = 1/10; Experiment III (adjuvant alone)-IFA = 8/10, silicone gel = 0/10. Anti-BII antibodies were formed in most of the rats treated with either silicone gel or IFA mixed with BII and these groups of rats showed a positive DTH reaction. The PBS treated rats were negative for both anti-BII antibodies and DTH reaction. Silicone gel taken from a commercial breast implant thus is capable of mediating collagen induced arthritis in the DA rat. However, silicone gel alone does not appear to be arthritogenic.

Hydrophobic, hydrophilic and other interactions in epitope-paratope binding.

Macroscopic, non-covalent, aspecific interactions between hydrophilic biopolymers, particles and cells in aqueous media tend to be repulsive; they are caused by Lifshitz-van der Waals (LW), Lewis acid-base (AB) and electrostatic (EL) forces. Microscopic scale specific interactions, e.g. between epitopes and paratopes, are also non-covalent and caused by attractive LW, AB and EL forces, which locally must be able to overcome the long- to medium-range macroscopic aspecific repulsive forces. Thus epitopes and paratopes need to be able to attract each other over a distance of at least 3 nm. The medium- and long-range specific attractive forces are mainly of hydrophobic (AB) and of EL origin; in aqueous media the medium- and long-range LW attractions are usually much weaker. It has been shown that hydrophobic (AB) interactions are as often enthalpic as entropic. Upon expulsion of interstitial water of hydration between epitope and paratope, a strong interfacial bond ultimately arises which is mainly caused by LW forces.

The effect of silicone-gel on the immune response.

Silicone materials have been used in medical applications for at least 30 years. Despite this long history of use the question whether silicones can mediate an immunological reaction that may be detrimental to the host remains unanswered. Most studies on the biocompatability of silicones conclude that silicones are chemically stable compounds, which however are often capable of eliciting a benign chronic inflammatory response. Recently, our laboratory has conducted a series of animal experiments aimed at determining the immunological adjuvancy potential of silicone-gel taken from commercial breast implants. Our previous studies have indicated that silicone-gel is a potent humoral (antibody) adjuvant. Our present studies have found that silicone-gel is capable of eliciting auto-antibodies to rat thyroglobulin and bovine collagen II. However this immune response did not produce any histological evidence of thyroiditis or arthritis. Theories to explain why silicone-gel behaves as an adjuvant are discussed along with discussion of the hypothesis on the desirability of replacing silicone-gel with a more hydrophilic material in bioimplants.

Inactivation of the Porphyromonas gingivalis fimA gene blocks periodontal damage in gnotobiotic rats.

Fimbrial production by Porphyromonas gingivalis was inactivated by insertion-duplication mutagenesis, using the cloned gene for the P. gingivalis major fimbrial subunit protein, fimA. by several criteria, this insertion mutation rendered P. gingivalis unable to produce fimbrilin or an intact fimbrial structure. A nonfimbriated mutant, DPG3, hemagglutinated sheep erythrocytes normally and was unimpaired in the ability to coaggregate with Streptococcus gordonii G9B. The cell surface hydrophobicity of DPG3 was also unaffected by the loss of fimbriae. However, DPG3 was significantly less able to bind to saliva-coated hydroxyapatite than wild-type P. gingivalis 381. This suggested that P. gingivalis fimbriae are important for adherence of the organism to saliva-coated oral surfaces. Further, DPG3 was significantly less able to cause periodontal bone loss in a gnotobiotic rat model of periodontal disease. These observations are consistent with other data suggesting that P. gingivalis fimbriae play an important role in the pathogenesis of human periodontal disease.

The adjuvant effect of silicone-gel on antibody formation in rats.

The extent of immunological adjuvancy of silicone-gel, from mammary implants, up to now, has not been determined definitively. This study compares the immune potentiation effects of silicone-gel with that of Freund's adjuvant, using bovine serum albumin (BSA) as the test antigen in rats. Sixty, 250 gr., male Sprague Dawley rats were divided into six groups: I- phosphate buffered saline (PBS) only, II- silicone oil (Dow Corning Medical Grade 360 liquid silicone), III- 50% silicone-gel (McGhan Medical Corp.- mammary implant) in silicone oil, IV- complete Freund's adjuvant (CFA), V- incomplete Freund's adjuvant (IFA), and VI- 50% silicone oil in IFA. Each adjuvant was mixed or emulsified with an equal volume of 50 micrograms of BSA in 150 microliters of PBS. Each immunization was given intramuscularly in a single injection. Cardiac puncture test bleeds were taken at 12, 22, 40 and 56 days post immunization and the serum anti-BSA-antibody was measured by ELISA. The results indicate that silicone-gel is a potent immunological adjuvant, compared to both CFA and IFA. Silicone oil alone is not as potent as adjuvant and seems to inhibit the immune response when mixed with IFA. There thus appears to be a distinct possibility that silicone-gel may also be able to mediate an auto-immune reaction.

The effect of hydrophilicity-hydrophobicity and solubility on the immunogenicity of some natural and synthetic polymers.

The general effects of solubility and hydrophobicity-hydrophilicity on the immunogenicity of synthetic and natural polymers are presented. The degree of hydrophobicity or hydrophilicity was determined from contact angle measurements. The surface tension components, obtained from the contact angles, were then correlated with the degree of immunogenicity for each substance. The results indicate that highly hydrophobic and highly hydrophilic polymers are not immunogenic. Moderate hydrophobicity as well as moderate hydrophilicity, and solubility in water favor immunogenicity (provided the molecular mass be at least 10,000 Da). For example, the solubilization of zein (a hydrophobic insoluble maize protein) prior to immunization causes zein to become immunogenic.

The effect of anti-tuftsin antibody on the phagocytosis of bacteria by human neutrophils.

Tuftsin (Thr-Lys-Pro-Arg) is a naturally occurring tetrapeptide which stimulates most known functions of the polymorphonuclear and mononuclear phagocytic cell lines. Although tuftsin is a well characterized bioactive peptide, the exact physiological role tuftsin plays remains unclear. Specific mouse anti-tuftsin antiserum generated in our laboratory, is now available for phagocytosis inhibition studies. Monolayers of human neutrophils were prepared on glass coverslips from a few drops of finger prick blood obtained from a single healthy donor. The monolayers were treated with and without mouse anti-tuftsin antiserum at dilutions of 1:1000 or 1:2000. Exogenous tuftsin (1 microgram/ml) was also added with and without antibody. Treated and untreated neutrophils were subsequently incubated with unopsonized Staphylococcus aureus. The proportion of cells accomplishing phagocytosis (phagocytic index) and the number of bacteria engulfed per cell (avidity index) were recorded. The results showed that exogenous tuftsin increased phagocytosis while the addition of mouse anti-tuftsin antiserum at a 1:1000 dilution inhibited phagocytosis both with and without exogenous tuftsin. This effect was diminished by the antiserum at the 1:2000 dilution. This study reaffirms that tuftsin plays an important physiological role in phagocytosis.