Electrostimulators for acupuncture: safety issues.

Three representative electrostimulators were evaluated to determine whether they meet the manufacturers' labeled nominal output parameters and how the measured parameters compare with a safety standard written for implanted peripheral nerve stimulators. The pulsed outputs (pulse width, frequency, and voltage) of three devices were measured with an oscilloscope across a 500-ohm resistance, meant to simulate subdermal tissue stimulated during electroacupuncture. For each device, at least two measured parameters were not within 25% of the manufacturer's claimed values. The measured values were compared with the American National Standard ANSI/AAMI NS15 safety standard for implantable peripheral nerve stimulators. Although for two stimulators the pulse voltage at maximum intensity was above that specified by the standard, short-term clinical use may still be safe because the standard was written for long-term stimulation. Similarly, the net unbalanced DC current, which could lead to tissue damage, electrolysis, and electrolytic degradation of the acupuncture needle, was within the limits of the standard at 30 pulses per second, but not at higher frequencies. The primary conclusions are (1) that the outputs of electrostimulators must be calibrated and (2) that practitioners must be adequately trained to use these electrostimulators safely.

Viral impermeability of hypoallergenic, low protein, guayule latex films.

Guayule latex proteins do not cross-react with antibodies raised against latex proteins in commercially available products manufactured from Hevea brasiliensis latex. Thus guayule latex is a promising raw material for the manufacture of hypoallergenic latex products, safe for use by people suffering from IgE-mediated Type I "latex allergy." Also, guayule latex is a low protein material and therefore unlikely to cause widespread sensitization. Latex products commonly are used as essential barriers against the transmission of disease, and so guayule hypoallergenic latex medical products would be a viable alternative only if they possess effective viral barrier properties. To address this question, fingers of prototype hand-dipped guayule latex examination gloves were tested for their permeability to a surrogate challenge virus, varphiX174. This virus has a diameter of 27 nm and is similar in size to the smallest human pathogenic viruses. Prototype guayule latex condom films were tested using synthetic blood over a range of pressures and, after 4 years of storage, with synthetic blood and with the varphiX174 virus. We concluded that guayule latex films taken from prototype hand-dipped gloves and condoms provide effective barriers to virus transmission and that they remain effective (at least in condoms) after long-term storage.

Implications of laboratory tests of condom integrity.

BACKGROUND: There is sufficient evidence from Food and Drug Administration laboratory experiments and clinical studies to draw conclusions about the relative importance of holes and breakage to condoms. The laboratory test methods determined penetration of viruses or virus-size microspheres through holes in condoms under conditions that simulated or exaggerated those expected in actual use, and determined the frequency with which condoms might pass virus or microspheres and the amounts of passage in each case. GOALS: To summarize and comment on the significance of test results on latex, polyurethane, and natural membrane condoms as barriers to virus passage. STUDY DESIGN: Published and unpublished data addressing three distinct concerns were analyzed: (1) passage of virus or microspheres through small holes or pores inherent in the material of "intact" condoms which are undetectable by the standard water leak quality assurance test, (2) passage of virus or microspheres through larger holes in "leaker" condoms detectable by the water leak test but marketed because of the finite acceptable quality level (AQL) of the test, and (3) passage of virus through condoms that break during use. RESULTS: Extrapolating to the passage of semen expected during actual use allowed an analysis of the relative importance of breakage and water-leak-detectable or water-leak-undetectable holes. CONCLUSIONS: The relative importance of breaks and holes is related to the volume of semen that contains an "infectious dose" of a sexually transmitted disease (STD). When 0.1 mL to 1.0 mL exposures to semen are necessary for disease transmission, the risk during latex condom use primarily results not from holes, but from breakage of condoms. For smaller volumes of semen exposure (0.00001 mL and less), the presence of holes can be as important as breaks. The same qualitative argument pertains to a comparison of "leaker" condoms to the large majority of "intact" condoms.

PIP: This study examines the significance of test results on latex, polyurethane, and natural membrane condoms as barriers to virus passage. Data on three distinct concerns were analyzed: 1) passage of virus or microspheres through small holes or pores inherent in the material of "intact" condoms which are undetectable by the standard water leak quality assurance test; 2) passage of virus or microspheres through larger holes in "leaker" condoms detectable by the leak test but marketed because of the finite acceptable quality level of the test; and 3) passage of virus through condoms that break during use. The results showed that relative importance of breaks and holes is related to the volume of semen that contains an "infectious dose" of a sexually transmitted disease. When 0.1-1.0 ml exposures to semen are necessary for disease transmission, the risk during latex condom use primarily results not from holes but from breakage of condoms. For smaller volumes of semen exposure (0.00001 ml or less), the presence of holes can be as important as breaks. The same qualitative argument pertains to a comparison of "leaker" condoms to the large majority of "intact" condoms.

Virus passage through track-etch membranes modified by salinity and a nonionic surfactant.

Why do viruses sometimes not pass through larger pores in track-etch filters? Increasing the salinity (0.8 to 160 mM Na+) decreased phiX174 and PRD1 passage through track-etch polycarbonate membranes (sodium dodecyl sulfate coated but not polyvinylpyrrolidone coated) and PRD1 passage through polyester membranes. Undiminished passage when 0.1% Tween 80 was added implied that nonionic virus adsorption occurred and indicated that high levels of salinity decreased virus passage by decreasing electrostatic repulsion that prevented adsorption.

Evaluation of endoscope sheaths as viral barriers.

OBJECTIVES: Evaluate ENT endoscope sheaths as barriers to virus passage. STUDY DESIGN: "Defective" sheaths covering an endoscope were challenged with virus to determine how many virus particles could be recovered from the endoscope. METHODS: Sheaths with small laser-drilled holes (2 to 30 microm) were challenged with high-titer virus suspensions (10(8) viruses/mL). The inside of the sheath and the endoscope were separately rinsed to recover any virus that penetrated through the hole in the sheath. In an attempt to assess the possible importance of holes in the sheaths, a sequential test was conducted with an initial virus challenge outside a defective sheath (30-micron hole in the sheath), after which the possibly contaminated endoscope was removed and inserted into a second defective sheath (with a 20-micron hole at the same location) to determine whether the contaminating virus would pass outward through the second sheath. RESULTS: Small volumes of virus-containing fluid penetrated through the hole, e.g., 500 virus particles passed through one of three 30-microm holes. A significant fraction of those virus particles was occasionally found on the endoscope after removal from the sheath. Similar results were obtained with sheaths that had small tears (34-84 microm in length, from punctures with fine wires). Although some virus penetration could occur during the initial challenge contaminating the endoscope, no virus was detected passing outward through the second sheath. CONCLUSIONS: Use of a sheath combined with intermediate level disinfection should provide a safe instrument for ENT endoscopy.

A mathematical model for simulating virus transport through synthetic barriers.

Synthetic barriers such as gloves, condoms and masks are widely used in efforts to prevent disease transmission. Due to manufacturing defects, tears arising during use, or material porosity, there is inevitably a risk associated with use of these barriers. An understanding of virus transport through the relevant passageways would be valuable in quantifying the risk. However, experimental investigations involving such passageways are difficult to perform, owing to the small dimensions involved. This paper presents a mathematical model for analyzing and predicting virus transport through barriers. The model incorporates a mathematical description of the mechanisms of virus transport, which include carrier-fluid flow, Brownian motion, and attraction or repulsion via virus-barrier interaction forces. The critical element of the model is the empirically determined rate constant characterizing the interaction force between the virus and the barrier. Once the model has been calibrated through specification of the rate constant, it can predict virus concentration under a wide variety of conditions. The experiments used to calibrate the model are described, and the rate constants are given for four bacterial viruses interacting with a latex membrane in saline. Rate constants were also determined for different carrier-fluid salinities, and the salt concentration was found to have a pronounced effect. Validation experiments employing laser-drilled pores in condoms were also performed to test the calibrated model. Model predictions of amount of transmitted virus through the drilled holes agreed well with measured values. Calculations using determined rate constants show that the model can help identify situations where barrier-integrity tests could significantly underestimate the risk associated with barrier use.

Mechanism of copper-mediated inactivation of herpes simplex virus.

The inactivation of herpes simplex virus (HSV) by copper was enhanced by the following reducing agents at the indicated relative level: ascorbic acid >> hydrogen peroxide > cysteine. Treatment of HSV-infected cells with combinations of Cu(II) and ascorbate completely inhibited virus plaque formation to below 0.006% of the infectious virus input, while it maintained 30% viability for the host mammalian cells. The logarithm of the surviving fraction of HSV mediated by 1 mg of Cu(II) per liter and 100 mg of reducing agent per liter followed a linear relationship with the reaction time, in which the kinetic rate constant for each reducing agent was -0.87 min(-1) (r = 0.93) for ascorbate, -0.10 min(-1) (r = 0.97) for hydrogen peroxide, and -0.04 min(-1) (r = 0.97) for cysteine. The protective effects of metal chelators and catalase, the lack of effect of superoxide dismutase, and the partial protection conferred by free-radical scavengers suggest that the mechanism of copper-mediated HSV inactivation is similar to that previously reported for copper-mediated DNA damage. The sensitivity exhibited by HSV to Cu(II) and reducing agents, particularly ascorbate, might be useful in the development of therapeutic antiviral agents.

An in vitro evaluation of condoms as barriers to a small virus.

BACKGROUND: Because of the possible presence of small holes, the effectiveness of condoms as barriers to virus transmission is controversial. GOALS: To determine the proportion of condoms that allow virus penetration and the amounts of virus that penetrate. STUDY DESIGN: A sensitive, static test was used to evaluate different condom types as barriers to a small virus, including brand with or without lubrication and ones of different materials. The test included some physiologic-based parameters and some parameters that exaggerated expected actual use conditions. RESULTS: Under test conditions, 2.6% (12 of 470) of the latex condoms allowed some virus penetration; the median level of penetration was 7 x 10(-4) ml. Lubricated condoms performed similarly to nonlubricated ones. Polyurethane condoms yielded results higher than but not statistically different from those for latex condoms. CONCLUSIONS: Few condoms allowed any virus penetration. The median amount of penetration for latex condoms when extrapolated to expected actual use conditions was 1 x 10(-5) ml (volume of semen). Thus, even for the few condoms that do allow virus penetration, the typical level of exposure to semen would be several orders of magnitude lower than for no condom at all.

PIP: Nine brands and 470 samples of latex condoms and two brands and 76 samples of polyurethane condoms bought from retail distributors were tested in vitro for their ability to block the penetration of virus. A sensitive, static test apparatus was designed for and used in the evaluation. The test included some physiological-based parameters as well as some which exaggerated the expected actual use conditions. Both lubricated and nonlubricated condoms were tested. Before testing, however, most of the lubrication was removed from the lubricated condoms through rinsing with Dulbecco's phosphate-buffered saline and blotting with sterile paper towels. The 0X174 bacteriophage of 27 nm particle diameter, 32 nm including its bulky spikes, was used as the proxy challenge virus. Under test conditions, 12 of the latex condoms (2.6%) allowed some virus penetration of median quantity 0.0007 ml. Just two of the latex condoms were responsible for 99.8% of the total penetration among latex condoms overall. The performance of lubricated condoms was similar to that of nonlubricated ones. Four of the polyurethane condoms allowed penetration, but only one condom was responsible for 98.6% of total penetration. The difference in performance between latex and polyurethane condoms is not statistically significant. The median amount of penetration for latex condoms when extrapolated to expected actual use conditions was 0.00001 ml of semen. Therefore, even for the few condoms which allow virus penetration, the typical level of exposure to semen is several orders of magnitude lower than the amount of exposure expected when not using a condom.

A sensitive method for evaluating condoms as virus barriers.

A standard test is needed to evaluate condoms as barriers against sexually transmitted diseases, particularly those caused by viruses. The proposed method presented here consists of a previously published simple method using physiologic-based conditions plus improvements to increase test sensitivity and decrease confounding factors such as contamination. Limitations of the method were determined by measuring virus penetration through small, well-defined holes. The method can detect penetration of 2 nL (2 x 10(-6) mL) of challenge virus suspension as well as a hole of 2 microns diameter in a latex condom. The data also indicated that virus penetration of latex condoms occurred quickly, and the hole was then apparently closed or blocked.

PIP: Condoms can act as barriers to the passage of sexually transmitted diseases (STDs). However, a claim that condoms are effective against STDs must be confirmed by appropriate laboratory tests. Various tests have therefore been developed to evaluate the barrier effectiveness of latex and natural membrane condoms. The authors describe and evaluate a test which involves filling the condom with virus-containing buffer and determining whether any virus penetrates the barrier during submersion in a collection buffer. Virus penetration is measured and reported as the equivalent volume of challenge virus suspension needed to account for the amount of virus penetration. The limitations of this approach were determined by measuring virus penetration through small, well-defined holes. It was found that the method can detect penetration of 2 nl of challenge virus suspension as well as a hole of 2 mcm diameter in a latex condom. The data also indicate that virus penetration of latex condoms occurs quickly, then the hole apparently closes or is blocked.

Elution of viruses by ionic and nonionic surfactants.

The ionic and nonionic surfactants sodium dodecyl sulfate and Triton X-100, respectively, eluted two viruses, phi X174 and PRD1, which were adsorbed to the ionic and nonionic binding membranes cationic polysulfone and nitrocellulose, respectively. Results indicated that complete elution was readily achieved only when combinations of surfactants and binding membranes were matched (i.e., ionic-ionic or nonionic-nonionic).

Minimized virus binding for tests of barrier materials.

Viruses are used to test the barrier properties of materials. Binding of virus particles during passage through holes in the material may yield misleading test results. The choices of challenge virus and suspending medium may be important for minimizing confounding effects that might arise from such binding. In this study, different surrogate viruses, as well as different support media, were evaluated to determine optimal test parameters. Two membranes with high-binding properties (nitrocellulose and cationic polysulfone) were used as filters to compare binding activities of different surrogate challenge viruses (MS2, phi X174, T7, PRD1, and phi 6) in different media. The media consisted of buffered saline with surfactants, serum, or culture broth as additives. In addition, elution rates of viruses that bound to the membranes were determined. The results suggest that viruses can bind by hydrophobic and electrostatic interactions, with phi X174 displaying the lowest level of binding by either process. The nonionic detergents Triton X-100 and Tween 80 (0.1%) equally minimized hydrophobic interactions. Neither anionic nor cationic surfactants were as effective at nontoxic levels. Serum was effective at reducing both hydrophobic and electrostatic binding, with 2% being sufficient for eliminating binding under our test conditions. Thus, phi X174 remains the best choice as a surrogate virus to test barrier materials, and Triton X-100 (0.1%) remains a good choice for reducing hydrophobic binding. In addition, binding of viruses by barrier materials is unlikely to prevent passage of blood-borne pathogens.

Herpes virus infection and repair in cells pretreated with gilvocarcin V or merocyanine 540 and radiation.

Pretreatment of mammalian cells with certain genotoxic agents decreases the ability of the cell monolayers to support virus plaque formation but enhances repair of UV-irradiated virus. This study was made to determine whether these phenomena extend to pretreatments with light and photosensitizers, including one dye that primarily affects cell membranes. Confluent CV-1 monkey kidney fibroblast monolayers were pretreated with either gilvocarcin V (GV) or merocyanine 540 (MC540) and light of appropriate wavelengths and infected with control or UV-irradiated herpes simplex virus (HSV). GV phototreatment is known to affect cells at the DNA level, and MC540 at the membrane level. UV radiation served as a positive control pretreatment. Phototoxic concentrations of GV and MC540 were determined via the capacity of pretreated cell monolayers to support plaque formation by unirradiated HSV. Parallel monolayer pretreatment and subsequent infection by UV-irradiated HSV demonstrated that both types of phototreatments enhanced virus survival, but the dose responses and time courses were different. The DNA-damaging GV phototreatment mimicked the effect of UV-irradiating the cells and produced delayed enhanced repair of UV-irradiated virus. However, the MC540-phototreatment produced enhancement of virus survival with a bimodal dose response pattern for immediate infection, suggesting a different route for affecting repair of damaged virus.

Antiviral activity of gilvocarcin V plus UVA radiation.

Gilvocarcin V (GV), a coumarin, is a nucleic acid photosensitizer that is phototoxic to bacteria and mammalian cells at picomolar levels in the presence of near-UV radiation (UVA). We evaluated the effectiveness of GV plus UVA for inactivation of several viruses, including herpes simplex virus, type 1 (HSV) and the bacterial viruses phi X174, T7, PRD1 and phi 6. Some inactivation of the bacterial viruses was observed with UVA radiation alone (4-50% survival at 26 kJ/m2). Additional photosensitized inactivation was observed only with T7 and phi 6 at 2.0 microM GV. On the other hand, HSV was photoinactivated with concentrations of GV three orders of magnitude lower (1.0 nM). Similar to the case with UV (254 nm) inactivation, the GV-UVA survival curve for HSV indicated multicomponent inactivation kinetics, which could not be explained by photobleaching of GV. The wide range of photosensitivities of these viruses to GV cannot be adequately explained by models based only on viral nucleic acid content or presence of lipid envelopes.

Virus inactivation by copper or iron ions alone and in the presence of peroxide.

Cupric and ferric ions were able to inactivate five enveloped or nonenveloped, single- or double-stranded DNA or RNA viruses. The virucidal effect of these metals was enhanced by the addition of peroxide, particularly for copper(II). Under the conditions of our test, mixtures of copper(II) ions and peroxide were more efficient than glutaraldehyde in inactivating phi X174, T7, phi 6, Junin, and herpes simplex viruses. The substances described here should be able to inactivate most, if not all, viruses that have been found contaminating medical devices.

An estimation of squamous cell carcinoma risk from ultraviolet radiation emitted by fluorescent lamps.

The risk of squamous cell carcinoma (SCC) from ultraviolet radiation (UV) emitted by unfiltered fluorescent lamps was assessed. The assessment employed a mathematical power model based on human epidemiological data, which relates the SCC incidence in the United States white population to ambient solar UV. The annual numbers of new SCC on anatomical sites chronically exposed to solar UV (head/face/neck and hands) were estimated for indoor workers. Then the number of SCC that may be caused by additional UV exposure from indoor fluorescent lighting was estimated: the lifetime exposure of indoor workers to typical fluorescent lighting (if unfiltered) may add 3.9% (1.6-12%) to the risk from solar UV, resulting in the induction of an additional 1500 (600-4500) SCC per annum in the United States. This calculated projection must be compared with the 110,000 SCC caused by solar exposure. Thus, this analysis suggests there may be a small increased risk of SCC from exposure to UV-emitting fluorescent lamps.

A simple method to test condoms for penetration by viruses.

A method by which virus penetration through condoms can be tested with simple, inexpensive equipment is described. The method uses chi X174 bacteriophage as the challenge virus and physiologically relevant pressure. Penetration by 0.1 microliters (or less) of challenge suspension can be readily detected. As examples, latex and natural-membrane condoms were examined.

Filtration sizes of human immunodeficiency virus type 1 and surrogate viruses used to test barrier materials.

Filters with well-defined holes were used to determine the effective diameters in buffer of human immunodeficiency virus type 1, herpes simplex virus type 1, and four bacteriophages (phi X174, T7, PRD1, and phi 6), which may serve as surrogate viruses for testing barrier materials. Bacteriophages phi 6 and PRD1 most closely model human immunodeficiency virus type 1 in filtration size.

Effects of two viral inactivation methods on platelets: laser-UV radiation and merocyanine 540-mediated photoinactivation.

Two viral inactivation methods suggested for use with cellular blood products have been evaluated as to their effects on platelets. In the first study, it was proposed that pulsed laser-ultraviolet radiation (UVB) at 308 nm could favor photodamage to UVB-sensitive viral nucleic acid with minimal effects on blood platelets. A "window of efficacy" was observed with UVB doses of 10.5-21.5 J/cm2 at which 4-6 log10 poliovirus were inactivated while platelets were relatively tolerant. However, this "window" occurred only with low-intensity UVB radiation (less than or equal to 0.25 MW/cm2). Damage to platelet proteins, evident at high laser intensities, was probably due to multiple photon excitation of amino acids. In the second study, platelets and viruses were treated with the photosensitizer, merocyanine 540 (MC 540) (less than or equal to 24 micrograms/ml), and visible light (450-600 nm) (less than or equal to J/cm2). Activation of washed platelets by dye/light treatment resulted in a spontaneous release of serotonin, spontaneous aggregation, and marked morphological changes. Increasing concentrations of albumin in the suspension medium protected against dye-mediated photodamage to platelets, but also significantly reduced the antiviral activity of MC 540 and light. These results illustrate the relative sensitivities of platelets and viruses to two inactivation methods and the difficulty in optimizing inactivation of viruses and preservation of platelet function in a protein-rich medium.

Important factors for testing barrier materials with surrogate viruses.

This study evaluated bacteriophages phi X174, T7, PRD1, and phi 6 as possible surrogates for pathogenic human viruses to challenge barrier materials and demonstrated some important factors for their use. Chemical incompatibility with test material was demonstrated when lipid-enveloped phi 6 was inactivated by an aqueous eluate of vinyl gloves, but 0.5% calf serum protected phi 6 from the eluate. Low concentrations (2%) of calf serum also prevented the exaggerated binding of the bacteriophages to filters. Recovery of viruses from surfaces decreased with increasing time before recovery. Penetration through punctures displayed different types of kinetics. The combined data indicate that (i) some bacteriophages may serve as surrogate viruses, (ii) experimental conditions determine whether a particular virus is appropriate as a challenge, and (iii) phi X174 is an excellent choice as a surrogate virus to test barrier materials. The data further indicate that before barrier materials are challenged with viruses, adequate tests should be performed to ensure that the virus is compatible with the test material and test conditions, so that meaningful data will result.