Effect Of Ultraviolet Treatment Research Articles

Effect of ultraviolet treatment on soft tissue healing and bacterial attachment to titania-coated zirconia.

Zirconia is the most promising implant abutment material due to its excellent aesthetic effect, good biocompatibility and corrosion resistance. To obtain ideal soft tissue sealing, the implant abutment surface should facilitate cell adhesion and inhibit bacterial colonization. In this study, pre-sintered zirconia was placed in a suspension of titania (TiO2) and zirconium oxychloride (ZrOCl2) and heated in a water bath for dense sintering. A titania coating was prepared on the zirconia surface and subjected to UV irradiation. The surface morphology, elemental composition and chemical state of each group of samples were analyzed by scanning electron microscope, x-ray energy spectrometer, x-ray photoelectron spectroscopy and x-ray diffraction. The responses of human gingival fibroblasts (HGFs) and common oral pathogensStreptococcus mutans(S. mutans) andPorphyromonas gingivalis(P. gingivalis) to modified zirconia were systematically assessed. Our findings demonstrated that the surface of titania-coated zirconia after UV irradiation produced a large number of hydroxyl groups, and its hydrophilicity was significantly improved. Meanwhile, the UV irradiation also greatly removed the hydrocarbon contaminants on the surface of the titania-coated zirconia. The UV-treated titania coating significantly promoted the proliferation, spreading, and up-regulation of adhesion-related genes and proteins of HGFs. Furthermore, the titania coating irradiated with UV could reduce the adhesion, colonization and metabolic activity ofS. mutansandP. gingivalis. Therefore, UV irradiation of titania-coated zirconia can promote the biological behavior of HGFs and exert a significant antibacterial effect, which has broad clinical application prospects for improving soft tissue integration around zirconia abutments.

A study on effects of curing and machining conditions in post-processing of SLA additive manufactured polymer

Stereolithography (SLA) is a promising additive manufacturing technology in terms of versatility and functionality. However, SLA-printed products lack mechanical properties and accuracy, so post-processing is essential. This study comprehensively contributes to a deeper understanding of influences of two types of post-processing [ultraviolet (UV) treatment and machining] and interactions between them. The effect of UV treatment was first investigated by evaluating properties of SLA specimens before and after UV curing. The UV curing greatly increased hardness by rearranging the molecular chains. The higher curing temperature, the denser and more uniform network was created; the surface hardness of the specimen cured at 80 °C increased by 208.30 % compared to the uncured specimen. Then, the interactions were analyzed by machining SLA specimens cured under different conditions. The pre-curing increased the hardness, molecular bonding, and brittleness. Thus, small surface roughness on the machined surface and small exit edge chipping were observed under the non-pre-curing conditions; the pre-curing increased the exit edge chipping size up to 48.21 %.

Effects of Ultraviolet Treatment and Alendronate Immersion on Osseointegration of Dental Implants and Mucosal Attachment of Dental Implant Abutments.

To evaluate the effects of ultraviolet (UV) treatment and alendronate immersion on the osseointegration of dental implants and mucosal attachment of dental implant abutments using a mongrel dog model. A total of 48 sandblasted, large-grit, acid-etched (SLA) titanium dental implants and 48 machined surface healing abutments in four male mongrel dogs were prepared. Implants and healing abutments were divided into four groups (n = 12 per group). The control (CON) group did not undergo additional surface treatments. The UV group was treated with UV for 15 minutes, and the alendronate-immersed (AN) group was soaked in 10-3 M alendronate for 24 hours. The UV treatment and alendronate soaking (UVAN) group was treated with alendronate, followed by UV irradiation. All implants were placed in the mandible of mongrel dogs, and the animals were sacrificed at 4 and 8 weeks postoperatively. Bone-to-implant contact (BIC), bone density, and connective tissue attachment were measured. In cortical bone, the UV group exhibited significantly higher BIC compared to the CON and AN groups (P < .05). In contrast, the AN and UVAN groups did not have significantly higher BIC. In the trabecular bone, there was no statistical difference between the groups. No significant increase in bone density and connective tissue attachment was shown in any group. UV treatment of SLA surface implants significantly increased osseointegration in cortical bone. The alendronate immersion did not increase osseointegration, and there was no synergic effect with UV treatment. Further, UV treatment and alendronate immersion of machined healing abutments did not significantly increase connective tissue attachment.

The Effect of Ultraviolet Treatment on TiO2 Nanotubes: A Study of Surface Characteristics, Bacterial Adhesion, and Gingival Fibroblast Response

Titanium dioxide (TiO2) nanotubes are emerging as a provocative target for oral implant research. The aim of this study was to evaluate the effect of UV on the wettability behavior, bacterial colonization, and fibroblast proliferation rate of TiO2 nanotube surfaces prepared using different anodization voltages and aimed for use as implant abutment materials. Four different experimental materials were prepared: (1) TiO2 nanotube 10 V; (2) TiO2 nanotube 15 V; (3) TiO2 nanotube 20 V; and (4) commercial pure titanium as a control group. TiO2 nanotube arrays were prepared in an aqueous electrolyte solution of hydrofluoric acid (HF, 0.5 vol.%). Different anodization voltages were used to modify the morphology of the TiO2 nanotubes. Equilibrium contact angles were measured using the sessile drop method with a contact angle meter. The investigated surfaces (n = 3) were incubated at 37 °C in a suspension of Streptococcus mutans (S. mutans) for 30 min for bacterial adhesion and 3 days for biofilm formation. Human gingival fibroblasts were plated and cultured on the experimental substrates for up to 7 days and the cell proliferation rate was assessed using the AlamarBlue assayTM (BioSource International, Camarillo, CA, USA). The data were analyzed using one-way ANOVA followed by Tukey’s post-hoc test. Water contact angle measurements on the TiO2 after UV treatment showed an overall hydrophilic behavior regardless of the anodization voltage. The ranking of the UV-treated surfaces of experimental groups from lowest to highest for bacterial adhesion was: TiO2 nanotube 20 V &lt; Ti and TiO2 nanotube 15 V &lt; TiO2 nanotube 10 V (p &lt; 0.05), and for bacterial biofilm formation was: TiO2 nanotube 20 V-TiO2 nanotube 10 V &lt; Ti-TiO2 nanotube 15 V (p &lt; 0.05). Fibroblast cell proliferation was lower on TiO2 nanotube surfaces throughout the incubation period and UV light treatment showed no enhancement in cellular response. UV treatment enhances the wettability behavior of TiO2 nanotube surfaces and could result in lower bacterial adhesion and biofilm formation.

Effect of ultraviolet treatment (UV–C) combined with nisin on industrialized orange juice in Alicyclobacillus acidoterrestris spores

Alicyclobacillus acidoterrestris is a bacteria capable of spoiling industrialized orange juice, making it a problem for the beverage industry. This study evaluated the effect of UV-C radiation in combination with nisin in the reduction of A. acidoterrestris spores using reconstituted orange juice. A. acidoterrestris spores were treated with nisin (7.81 and 15.62 μg/mL) in combination with different doses of UV-C (from 2.52 to 12.6 kJ/m2). The presence of vitamins in the juice after the treatments was investigated by UHPLC-HRMS using a ultra high performance liquid chromatography system. The combination of UV-C and nisin treatment showed counts below the detection limit of the method (<1.7 log CFU/mL) both at time 6 min (5.04 kJ/m2) with 7.81 μg/mL nisin and at time 3 min (2.52 kJ/m2) with 15.62 μg/mL nisin (p < 0.05). Ascorbic acid was found in control and 3-min UV-C samples, but with 15 min of treatment the vitamin was not detected. Thiamine was found in the three samples analyzed (T0, T3 and T15). Treatment with UV-C combined with low dose nisin (2.52 kJ/m2) eliminated spores without degrading the analyzed juice vitamins and is a promising alternative for the beverage industry.

Effect of ultraviolet treatment on shelf life of fresh lotus root.

The potential use of ultraviolet (UV)-C (254nm) to extend postharvest shelf life of fresh unprocessed lotus root (Nelumbo nucifera G.) was determined. UV treatment for 30 and 60min effectively reduced weight loss, improved moisture, color retention, and soluble solids of samples when stored at 25°C for 15days. Microbial growth inhibition of UV was evidenced by 1.8 and 1.0 log reductions in the 30 and 60min-treated samples. Phenylalanine ammonia lyase (PAL) activity and total phenol contents (TPCs) detected in lotus root were higher, while oxidative enzymes peroxidase (POD) and polyphenol oxidase (PPO) were inhibited by UV treatment. Gallic acid, gallocatechin, and catechin levels were increased in 30min-treated samples by about 0.9, 13.4, 8.0mg/100g. The results suggest that extension of postharvest storage life by UV-C is most likely through the protective roles exerted from stimulation of the phenylpropanoid pathway in the treated roots. PRACTICAL APPLICATIONS: Unlike previous studies that are mainly focused on shelf life extension of processed products of the rhizome, this study determines the potential use of a nonchemical and ecologically friendly ultraviolet (UV-C) treatment to extend shelf life of intact uncut fresh lotus root. Our results demonstrated that UV-C treatment significantly prolonged the shelf life of lotus root. Use of this method is promising as a treatment to improve postharvest storage life of fresh lotus root, to improve its export potential and help to address unmet local demands for the crop.

Effects of ultraviolet treatment and alendronate immersion on osteoblast-like cells and human gingival fibroblasts cultured on titanium surfaces

In this study, we evaluated the effects of ultraviolet (UV) treatment and alendronate (ALN) immersion on the proliferation and differentiation of MG-63 osteoblast-like cells and human gingival fibroblasts (HGFs) cultured on titanium surfaces. MG-63 cells were used for sandblasted, large grit, and acid-etched (SLA) titanium surfaces, and HGFs were used for machined (MA) titanium surfaces. SLA and MA specimens were subdivided into four groups (n = 12) according to the combination of surface treatments (UV treatment and/or ALN immersion) applied. After culturing MG-63 cells and HGFs on titanium discs, cellular morphology, proliferation, and differentiation were evaluated. The results revealed that UV treatment of titanium surfaces did not alter the proliferation of MG-63 cells; however, HGF differentiation and adhesion were increased in response to UV treatment. In contrast, ALN immersion of titanium discs reduced MG-63 cell proliferation and changed HGFs into a more atrophic form. Simultaneous application of UV treatment and ALN immersion induced greater differentiation of MG-63 cells. Within the limitations of this cellular level study, simultaneous application of UV treatment and ALN immersion of titanium surfaces was shown to improve the osseointegration of titanium implants; in addition, UV treatment may be used to enhance mucosal sealing of titanium abutments.

Effect of ultraviolet treatment on bacterial attachment and osteogenic activity to alkali-treated titanium with nanonetwork structures.

PurposeAlkali-treated titanium with nanonetwork structures (TNS) possesses good osteogenic activity; however, the resistance of this material to bacterial contamination remains inadequate. As such, TNS implants are prone to postoperative infection. In this work, we attempted to alter the biological properties of TNS by treatment with short-duration high-intensity ultraviolet (UV) irradiation.MethodsTNS discs were treated with UV light (wavelength =254 nm, strength =100 mW/cm2) for 15 minutes using a UV-irradiation machine. We carried out a surface characterization and evaluated the discs for bacterial film formation, protein adsorption, and osteogenic features.ResultsThe superhydrophilicity and surface hydrocarbon elimination exhibited by the treated material (UV-treated titanium with a nanonetwork structure [UV-TNS]) revealed that this treatment effectively changed the surface characteristics of TNS. Notably, UV-TNS also showed reduced colonization by Actinomyces oris during an initial attachment period and inhibition of biofilm formation for up to 6 hours. Moreover, compared to conventional TNS, UV-TNS showed superior osteogenic activity as indicated by increased levels of adhesion, proliferation, alkaline phosphatase activity, osteogenic factor production, and osteogenesis-related gene expression by rat bone marrow mesenchymal stem cells (rBMMSCs). This inverse relationship between bacterial attachment and cell adhesion could be due to the presence of electron–hole pairs induced by high-intensity UV treatment.ConclusionWe suggest that simple UV treatment has great clinical potential for TNS implants, as it promotes the osseointegration of the TNS while reducing bacterial contamination, and can be conducted chair-side immediately prior to implantation.

The effect of ultraviolet treatment on enzymatic activity and total phenolic content of minimally processed potato slices.

In this work, potato slices were exposed to different doses of UV-C irradiation (i.e. 2.28, 6.84, 11.41, and 13.68kJm-2) with or without pretreatment [i.e. ascorbic acid and calcium chloride (AACCl) dip] and stored at 4±1°C. Changes in enzymatic activities of polyphenol oxidase (PPO), peroxidase (POD) and phenylalanine ammonia lyase (PAL), as well as total phenolic content (TPC) were investigated after 0, 3, 7 and 10days of storage. Results showed that untreated and UV-C treated potato slices at 13.68kJm-2 dosage level showed significantly higher PPO, POD and PAL activities. Conversely, untreated potato slices showed the lowest TPC during storage period. Potato slices subjected to AACCl dip plus UV-C at 6.84kJm-2 produced lower PPO, POD and PAL activities, as well as maintained a high TPC during storage.

Effects of storage medium and UV photofunctionalization on time-related changes of titanium surface characteristics and biocompatibility.

Storage in aqueous solution and ultraviolet (UV) photofunctionalization are two applicable methods to overcome the biological aging and increase the bioactivity of titanium. As information regarding the combined effects of storage medium and UV photofunctionalization has never been found in published literatures, this study focused on whether appropriate storage methods and UV photofunctionalization have synergistic effects on the biological properties of aged titanium surfaces. Titanium plates and discs were sandblasted and acid etched and then further prepared in five different modes as using different storage mediums (air or dH2 O) for 4 weeks and then with or without UV treatment. The surface characteristics were evaluated with scanning electron microscopy, contact angle measurements, and X-ray photoelectron spectroscopy. MC3T3-E1 cells were cultured on the surfaces, and cellular morphology, proliferation, alkaline phosphatase activity, and osteocalcin release were evaluated. The results showed that nanostructures were observed on water-stored titanium surfaces with a size of about 15 × 20 nm(2) . UV treatment was effective to remove the hydrocarbon contamination on titanium surfaces stored in either air or water. UV photofunctionalization further enhanced the already increased bioactivity of modSLA on initial cell attachment, proliferation, alkaline phosphatase activity, and osteocalcin release. Overall, UV photofunctionalization was effective in further enhancing the already increased bioactivity by using dH2 O as storage medium, and the effect of UV treatment was much more overwhelming than that of the storage medium. © 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 104B: 932-940, 2016.

The Effect of UV treatment on the recovery characteristics of a-IGZO-based thin film transistors

We investigated the effects of ultraviolet (UV) treatment on the negative bias illumination stress (NBIS) and the recovery characteristics of amorphous indium-gallium-zinc-oxide (a-IGZO)-based transparent thin-film transistors (TTFTs). We developed TTFTs with a top gate structure that used a-IGZO and Al2O3 films for the active layer and the gate dielectric, respectively. The developed TTFTs were under NBIS in air at room temperature (RT) at wavelengths of 190–517 nm. For the devices with NBIS that had been treated with visible light (wavelength (λ) < 414 nm), the NBIS-induced instability is attributed to the combined effects of subgap-assisted electron generation via ionized oxygen vacancies (V o 2+) in IGZO and hole trapping near the IGZO/Al2O3 interface via both V o 2+- and V o -mediated electron-hole pair creation. At lower λ, the devices under NBIS showed slower recovery characteristics, which were attributed to the stronger stabilization of V o 2+ near the IGZO/Al2O3 interface at RT.

Ecological responses to UV radiation: interactions between the biological effects of UV on plants and on associated organisms.

Solar ultraviolet (UV)-B radiation (280-315 nm) has a wide range of effects on terrestrial ecosystems, yet our understanding of how UV-B influences the complex interactions of plants with pest, pathogen and related microorganisms remains limited. Here, we report the results of a series of experiments in Lactuca sativa which aimed to characterize not only key plant responses to UV radiation in a field environment but also consequential effects for plant interactions with a sap-feeding insect, two model plant pathogens and phylloplane microorganism populations. Three spectrally modifying filters with contrasting UV transmissions were used to filter ambient sunlight, and when compared with our UV-inclusive filter, L. sativa plants grown in a zero UV-B environment showed significantly increased shoot fresh weight, reduced foliar pigment concentrations and suppressed population growth of green peach aphid (Myzus persicae). Plants grown under a filter which allowed partial transmission of UV-A radiation and negligible UV-B transmission showed increased density of leaf surface phylloplane microbes compared with the UV-inclusive treatment. Effects of UV treatment on the severity of two plant pathogens, Bremia lactucae and Botrytis cinerea, were complex as both the UV-inclusive and zero UV-B filters reduced the severity of pathogen persistence. These results are discussed with reference to known spectral responses of plants, insects and microorganisms, and contrasted with established fundamental responses of plants and other organisms to solar UV radiation, with particular emphasis on the need for future integration between different experimental approaches when investigating the effects of solar UV radiation.

Effect of photoreactivation on ultraviolet inactivation of Microcystis aeruginosa

Microcystis aeruginosa forms algal bloom in lakes. They produce toxic compounds such as microcystin. Against such algal problems, the effect of UV treatment was examined. In UV treatment, the effect of photoreactivation should be examined. Photoreactivation is a repair mechanism of genomic DNA damage by sunlight irradiation. UV treatment causes DNA damages on target cyanobacteria, however sunlight can repair some of these DNA damages. To examine the effect of photoreactivation, both white and yellow light incubations were employed. White light allows both photoreactivation and photosynthesis, while yellow light prohibits photoreactivation and only allows photosynthesis. Microcystis aeruginosa NIES 98 strain and PCC 7806 strain were used as the test cultures. Those cultures were exposed to low-pressure (LP) or medium-pressure (MP) ultraviolet (UV) lamp, then incubated under white or yellow light. Yellow light incubation method was effective to examine photoreactivation. It was revealed that almost six times UV fluence was required to inactivate 99% of Microcystis aeruginosa, under photoreactivation condition, compared with non-photoreactivation condition. Inhibition of photoreactivation could greatly enhance UV treatment efficiency against Microcystis aeruginosa. One of the practical suggestions is to conduct UV treatment at night, when photoreactivation by sunlight rarely takes place. Highly efficient inactivation was achieved by avoiding photoreactivation.

Effects of ultraviolet treatment on the photovoltaic property of poly(3,4-ethylenedioxythiophene) doped with poly(4-styrenesulfonate)/n-type Si diodes

In this study, the effect of ultraviolet treatment on the photovoltaic property of poly(3,4-ethylenedioxythiophene) doped with poly(4-styrenesulfonate)/n-type Si (PEDOT:PSS/n-Si) diodes was examined. Power conversion efficiency of the PEDOT:PSS/n-Si diodes in the light (AM 1.5G, 100 mW/cm 2) was improved by reducing the device series resistance by ultraviolet treatment. This study shows that conductivity of PEDOT:PSS plays an important role in PEDOT:PSS/n-Si photovoltaic devices.

Effect of UV treatment on DBP formation

This study—s objective was to investigate the effect of ultraviolet (UV) treatment on the subsequent formation of regulated and unregulated disinfection by‐products (DBPs). UV treatment of two sets of waters did not substantially change the waters— tendency to form trihalomethanes, haloacetic acids, or total organic halogen under the conditions of these tests. Evidence was found of small reductions in the formation of these DBPs, but the decreases did not exceed 10%. Formation of chloropicrin and 1,1,1‐trichloropropanone increased as a result of medium‐pressure UV treatment but remained at levels well below those of the regulated DBPs. Low‐pressure UV did not cause any detectable increase in chloropicrin formation. The authors propose that photonitration leads to the formation of new nitroorganics during UV treatment and these form halonitromethanes during subsequent chlorination. It is recommended that the effects of UV treatment on nonregulated DBPs be considered as new UV drinking water systems are brought on line.

Band bending at the conducting polymer/indium tin oxide interfaces with and without ultraviolet treatment

In this study, the effect of ultraviolet treatment on the band bending at the poly(3,4-ethylenedioxythiophene) doped with poly(4-styrenesulfonate)/indium tin oxide (PEDOT:PSS/ITO) interfaces were researched. The authors suggested that ultraviolet treatment could lead to a reduction in the band bending at the PEDOT:PSS/ITO interface, owing to the removal of carbon contamination at the ITO surfaces and a decrease in the number of the trap-states at the PEDOT:PSS/ITO interface.

Effects of ultraviolet treatment on the contact resistivity and electronic transport at the Ti/ZnO interfaces

We report on the effect of ultraviolet (UV) treatment on the specific contact resistance (ρ) and electronic transport at the Ti/ZnO interfaces. The experimental results show the same barrier height of Ti/ZnO samples without UV treatment as Ti/ZnO samples with UV treatment and the higher ρ of Ti/ZnO samples with UV treatment than Ti/ZnO samples without UV treatment, suggesting the barrier-height independence of ρ. Based on the thermionic-emission model and x-ray photoelectron spectroscopy results, we found that the induced decrease in the number of the hydroxides at the surface region of ZnO by UV treatment resulted in decreases in the electron concentration near the surface region and the excess current component related to tunneling, increasing in ρ of Ti/ZnO samples.

Multiple Keratoacanthomas Arising Post-UVB Therapy

Background: Ultraviolet (UV) radiation is known to be an important etiologic agent in the development of skin cancer. Keratoacanthoma is an unusual, well-described cutaneous neoplasm that resembes squamous cell carcinoma but spontaneously resolves. Rarely, multiple keratoacanthomas may develop. Objective We present a case of multiple keratoacanthomas in a patient with psoriasis who had received UVB phototherapy. These lesions were hyperkeratotic papules, many of which spontaneously resolved and demonstrated the histologic characteristics of keratoacanthoma. Conclusion: We believe that UV radiation is the most likely etiologic factor in this patient's development of multiple keratoacanthomas. We wish to bring to the attention of clinicians this unusual adverse effect of UV treatment.

Effects of UV treatment on the proline-linked pentose phosphate pathway for phenolics and L-DOPA synthesis in dark germinated Vicia faba

Fava beans ( Vicia faba) have a high phenolic content. Antioxidant properties of phenolics are extensively studied for their ability to inhibit lipid oxidation in food and for improved health. This legume has the potential to be an effective dietary source of polyphenolics for health. The rationale behind this study was to observe the stimulation of nutraceutically relevant phenolic metabolites when germinating fava beans are exposed to ultra violet (UV) and the potential role of the proline-linked pentose phosphate pathway (PPP). Studies have shown phenolic phytochemicals can be stimulated with UV light. The objective was to over-express the PPP through the regulation of the key enzyme, glucose-6-phosphate dehydrogenase (G6PDH), for enhanced phenolics and L-DOPA production and investigate the link to proline metabolism. Guaiacol peroxidase (GPX) activity was monitored to understand the extent to which the UV-stimulated phenolics could be converted to polymeric phenols. L-DOPA is the precursor of dopamine (DA), the neuromodulator and used for treatment of Parkinson's disease. Seeds of fava beans were pretreated in water, exposed to 5, 10 and 15 h UV light and germinated for 8 days in dark. Total phenolics, proline levels and enzyme activities were measured spectrophotometrically. L-DOPA was measured by High-performance liquid chromatography (HPLC). A total of 15 h UV treatment stimulated L-DOPA on day 1, which reduced over next 8 days of germination. Antioxidant activity of the total phenolic acids was determined by inhibition of the β-carotene oxidation and there was stimulation of antioxidant activity in response to 10 h UV treatment on day 2. Total phenolic content increased 10-fold after 15 h UV light exposure on day 6 along with the highest activity of G6PDH. All treatments stimulated GPX activity indicating polymerization of free phenolics in the late stage of germination. Proline levels were also stimulated in response to all treatments. The stimulation of proline concurrent with stimulation of G6PDH and total phenolics in response to 15 h UV indicates a role of proline-linked PPP. Results indicate an increase in nutraceutically-relevant phenolic metabolites along with enhanced antioxidant activity in response to UV stress. This novel approach provides a mechanism to understand and enhance biosynthesis of important phenolic compounds in plant and legume systems for use in nutraceutical applications.

Seminal plasma superoxide dismutase activity following radiotherapy: Protection by the exogenous enzyme and effects of intracellular inhibition

For referred subfertile, radiation-exposed and known fertile males seminal plasma superoxide dismutase activity did not correlate with sperm density, % sperm motility, sperm velocity or penetration in the sperm penetration assay (SPA), but was found to correlate positively with seminal plasma zinc. A study of seminal plasma superoxide dismutase in relation to post-irradiation clinical treatment time provided tentative evidence that following a radiation challenge, superoxide dismutase might be subject to induction. When sperm intracellular superoxide dismutase was inhibited by incubation with diethyldithiocarbamate (DDC) in defined culture medium, motility ceased within 30 min but there was no associated rise in lipid peroxidation. Sperm pretreatment with DDC at concentrations as low as 10 μ m could abolish penetration in the SPA provided sperm were prepared by passive incubation. Cells electropermeabilized in the presence of calcium could overcome the DDC block. Exogenous addition of superoxide dismutase and catalase could provide effective protection to sperm against the effects of ultraviolet treatment.