The inhibitory and bactericidal concentrations of electrically generated silver ions were 10 to 100 times lower than for silver sulfadiazine. Effects on normal mammalian cells were minimal.

Silver, platinum, gold, stainless-steel, and copper electrodes were used with low currents (0.02 to 20'gA/mm2) to explore their electrochemical effects on the growth of four bacterial species. In the higher current ranges, all electrodes inhibited growth at both poles, usually in conjunction with electrolytic breakdown of the medium and severe corrosion of the metal. Silver, however, was extremely bacteriostatic, even at the lowest current, when used as the anode. Quantitative studies showed that most of this inhibition takes place in a few hours and is not accompanied by changes in pH. Electrochemically injected silver from the anode is probably the instrumental agent, being effective in conc,entrations of about 5 lAg/ml. This is the equivalent concentration of silver sulfadiazine that has been shown to give complete inhibition of bacteria, but without the sulfonamide moiety.The inhibition of bacterial multiplication by use of electric currents and metal electrodes has been reported (3,5,6,8). Whether alternating or direct currents were used, most authors agree that electrochemical products at the electrodes and/or metal ions are instrumental in this effect. In most cases, however, the currents were high enough to produce severe changes in the medium, especially near the electrodes.The present study was undertaken to explore the effects of relatively weak direct currents (and their electrochemical products) on agar plate bacterial cultures of Staphylococcus aureus, Escherichia coli, Proteus vulgaris, and Pseudomonas aeruginosa. Attention is paid to: (i) the electrode metal, (ii) the surface current density at the electrode, and (iii) the spatial character and polarity of the effects. We also report the results of more detailed measurements of viable organisms in the region of silver electrodes in liquid broth cultures as a function of time, current, and polarity.In a preliminary study (1) on S. aureus, it was found that currents of the order of 10-8 A/mm2 with silver electrodes can give rise to significant local inhibition. Much higher currents were required for platinum, gold, and stainless steel, usually in association with the breakdown of the electrolyte, to achieve similar effects. MATERIALS AND METHODSQualitative studies. Culture plates (45 mm) were prepared by mixing 0.5 ml of broth medium (GIBCO 1-t-1859) containing exponential-phase bacteria (optical density of 0.17 to 0.23 at 500 nm) with 3 ml of nutrient agar (GIBCO 1-t-1904) at 48 C. Identical electrode pairs (20 by 0.2 to 0.4 mm) were included in the plates and emerged through the sides. Pure silver (99.99%), platinum (99.9%), gold (99.99%), surgical stainless-steel (no. 316L), or copper (99.99%) wires were used. Battery-operated, constant-current generators (modifications of Vitron LIDC generators kindly supplied by Jack TerBeek of the Ritter Co., Rochester, N.Y.) were applied to the electrodes (except controls) after solidification of the agar and throughout incubation (37 C, 24 h). Current levels were 0.4, 4.0, 40, and 400 uA. In some cases the ...

Fractures of the distal radius are common, especially in postmenopausal women, and their prevalence increases with age. Knowledge of the factors that increase the risk of fracture in this metaphyseal region would have predictive and therapeutic implications. Of particular interest in this study were (a) the relative contributions of cortical and trabecular bone to the strength of the distal radius and (b) the best radiographic features to use as strength indicators. In 21 forearms from fresh cadavera (median age at the time of death, 75 years), single photon absorptiometry and quantitative computed tomography were used to determine bone mineral content (BMC), density (BMC/W), and cross-sectional properties of the radius at distal and midshaft sites. Mechanical testing of the forearms then was used to determine the ultimate force and energy to cause the type of fracture that might be caused by a fall on the outstretched hand. Twelve of the 17 tested specimens sustained a fracture of the distal radius, and five sustained a fracture of the scaphoid. In the group of fractures of the distal radius, we found the cross-sectional area and moment of inertia of the cortical shell at the metaphyseal site to be better correlates of strength than the trabecular area and trabecular moment. In contrast, strength correlated much better with trabecular density than with cortical density. Overall, the best correlates of strength were the BMC and BMC/W at either the distal or proximal site. On balance, these results suggest that the thin cortical shell contributes substantially more to the mechanical strength of the distal radius than has been commonly appreciated.

A qualitative and quantitative investigation was undertaken to study the susceptibility of unicellular eucaryotic organisms (yeasts) to metallic cations generated by low levels of direct current. Results were characteristic of effects obtained previously using clinical and standard bacteria test organisms. The present study demonstrated that anodic silver (Ag+) at low direct currents had inhibitory and fungicidal properties. Broth dilution susceptibility tests were made on several species of Candida and one species of Torulopsis. Growth in all isolates was inhibited by concentrations of electrically generated silver ions between 0.5 and 4.7 mg/ml, and silver exhibited fungicidal properties at concentrations as low as 1.9 ,ug/ml. The inhibitory and fungicidal concentrations of electrically generated silver ions are lower than those reported for other silver compounds.We have previously examined the bactericidal activities of a variety of metallic ions generated from pure metallic anodes by direct currents. We reported (3, 4, 11) that the silver ion was an effective antibacterial agent when liberated by low levels of direct current. Quantitatively it was more effective against both grampositive and gram-negative organisms than silver sulfadiazine. All other metals tested lacked bactericidal properties except when associated with high levels of direct current (400 ,uA) and the accompanying major pH changes.Lukens (6) reviewed the work of S. E. A. McCallan and F. Wilcoxon, who examined the fungitoxicity of the elements in relation to their position in the periodic table. Generally, toxicity within a group increased with atomic weight. Silver and osmium were the most toxic elements. Data from J. G. Horsfall have been summarized (7) and show that metals are arranged in the following descending order of fungitoxicity:

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