Bacterial adhesion on titanium implant surfaces has a strong influence on healing and long-term outcome of dental implants. Parameters like surface roughness and chemical composition of the implant surface were found to have a significant impact on plaque formation. The purpose of this study was to evaluate the influence of two physical hard coatings on bacterial adhesion in comparison with control surfaces of equivalent roughness. Two members of the oral microflora, Streptococcus mutans and Streptococcus sanguis were used. Commercially pure titanium discs were modified using four different surface treatments: physical vapour deposition (PVD) with either titanium nitride (TiN) or zirconium nitride (ZrN), thermal oxidation and structuring with laser radiation. Polished titanium surfaces were used as controls. Surface topography was examined by SEM and estimation of surface roughness was done using a contact stylus profilometer. Contact angle measurements were carried out to calculate surface energy. Titanium discs were incubated in the respective bacterial cell suspension for one hour and single colonies formed by adhering bacteria were counted by fluorescence microscopy. Contact angle measurements showed no significant differences between the surface modifications. The surface roughness (Ra) of all surfaces examined was between 0.14 and 1.00 microm. A significant reduction of the number of adherent bacteria was observed on inherently stable titanium hard materials such as TiN and ZrN and thermically oxidated titanium surfaces compared to polished titanium. In conclusion, physical modification of titanium implant surfaces such as coating with TiN or ZrN may reduce bacterial adherence and hence improve clinical results.

Until now, the general importance of microvilli present on the surface of almost all differentiated cells has been strongly underestimated and essential functions of these abundant surface organelles remained unrecognized. Commonly, the role of microvilli has been reduced to their putative function of cell-surface enlargement. In spite of a large body of detailed knowledge about the specific functions of microvilli in sensory receptor cells for sound, light, and odor perception, their functional importance for regulation of basic cell functions remained obscure. Here, a number of microvillar mechanisms involved in fundamental cell functions are discussed. Two structural features enable the extensive functional competence of microvilli: First, the exclusive location of almost all functional important membrane proteins on microvilli of differentiated cells and second, the function of the F-actin-based cytoskeletal core of microvilli as a structural diffusion barrier modulating the flow of low molecular substrates and ions into and out of the cell. The specific localization on microvilli of important functional membrane proteins such as glucose transporters, ion channels, ion pumps, and ion exchangers indicate the importance and diversity of microvillar functions. In this review, the microvillar mechanisms of audioreceptor, photoreceptor, and olfactory/taste receptor cells are discussed as highly specialized adaptations of a general type of microvillar mechanisms involved in regulation of important basic cell functions such as glucose transport/energy metabolism, ion channel regulation, generation and modulation of the membrane potential, volume regulation, and Ca signaling. Even the constitutive cellular defence against cytotoxic compounds, also called "multidrug resistance (MDR)," is discussed as a microvillar mechanism. A comprehensive examination of the specific properties of "cable-like" ion conduction along the microvillar core structure of F-actin allows the proposal that microvilli are specifically designed for using ionic currents as cellular signals. In view of the multifaceted gating and signaling properties of TRP channels, the possible role of microvilli as a universal gating device for TRP channel regulation is discussed. Combined with the role of the microvillar core bundle of actin filaments as high-affinity Ca store, microvilli may turn out as highly specialized Ca signaling organelle involved in store-operated Ca entry (SOCE) and initiation of nonlinear Ca signals such as waves and oscillations.

Gartzke, Joachim, and Klaus Lange. Cellular target of weak magnetic fields: ionic conduction along actin filaments of microvilli. Am J Physiol Cell Physiol 283: C1333-C1346, 2002; 10.1152/ajpcell. 00167.2002.-The interaction of weak electromagnetic fields (EMF) with living cells is a most important but still unresolved biophysical problem. For this interaction, thermal and other types of noise appear to cause severe restrictions in the action of weak signals on relevant components of the cell. A recently presented general concept of regulation of ion and substrate pathways through microvilli provides a possible theoretical basis for the comprehension of physiological effects of even extremely low magnetic fields. The actin-based core of microfilaments in microvilli is proposed to represent a cellular interaction site for magnetic fields. Both the central role of F-actin in Ca 2ϩ signaling and its polyelectrolyte nature eliciting specific ion conduction properties render the microvillar actin filament bundle an ideal interaction site for magnetic and electric fields. Ion channels at the tip of microvilli are connected with the cytoplasm by a bundle of microfilaments forming a diffusion barrier system. Because of its polyelectrolyte nature, the microfilament core of microvilli allows Ca 2ϩ entry into the cytoplasm via nonlinear cable-like cation conduction through arrays of condensed ion clouds. The interaction of ion clouds with periodically applied EMFs and field-induced cation pumping through the cascade of potential barriers on the F-actin polyelectrolyte follows well-known physical principles of ion-magnetic field (MF) interaction and signal discrimination as described by the stochastic resonance and Brownian motor hypotheses. The proposed interaction mechanism is in accord with our present knowledge about Ca 2ϩ signaling as the biological main target of MFs and the postulated extreme sensitivity for coherent excitation by very low field energies within specific amplitude and frequency windows. Microvillar F-actin bundles shielded by a lipid membrane appear to function like electronic integration devices for signal-tonoise enhancement; the influence of coherent signals on cation transduction is amplified, whereas that of random noise is reduced. calcium signaling; cell differentiation; Brownian motor hypothesis; cyclotron resonance; hair cell; mechanoelectrical coupling; physiological effects MORE THAN A DECADE OF RESEARCH on field effects in biological systems has yielded rather compelling data for the involvement of the Ca 2ϩ signaling pathway as a primary and main target of magnetic fields (MFs). As first demonstrated by Liburdy and colleagues (52,53) and later on by a number of other authors, the Ca 2ϩ influx pathways of isolated or cultured cells are severely affected by rather low MF energies.The physiological relevance of this finding is high, because Ca 2ϩ represents the most important intracellular signal governing almost all physiological functions in differentiated cells. Most importantly, cytopla...

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