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Reported instances of stable nonflow in He II Josephson effect experiments have in most cases been achieved by a flow of liquid helium from one reservoir to another, a flow driven by ultrasonic pumping. We have examined some of the characteristics of this pumping. We confirm that a threshold transducer power is necessary to initiate pumping and find that the threshold power has a temperature dependence of ρsTα, 0 < α < 1, in the range 1.5 K < T < 2.1 K. A capacitor has always been used by others to measure the meniscus level. We find that the geometry of the core of this capacitor is important: when the core bottom is conical, with vertex pointing down, we achieve no pumping. We find that the orientation of an asymmetric pinhole plays no role. Finally, the pumping speed is a monotonic function of transducer power for powers exceeding threshold and for powers less than an upper limit, above which there is no further increase in pumping speed. [ABSTRACT FROM AUTHOR]

Most aspects of acoustic streaming were considered understood in 1954. The time dependence of its onset, however, was controversial when Liebermann's measurements, valid for slowly developing streaming, were criticized. The criticism cited a report that streaming was present only 20 msec after turning on the acoustic source. Using a thermistor bead as flow meter, we have observed the time dependence of the onset of streaming in two fluids of widely different viscosity, each in two vessels of different geometry. The time dependence of the streaming velocity is described as follows: There is zero time derivative at the start. This is followed in succession by a positive second derivative, inflection point, and negative second derivative which persists during an approach to a steady state flow. From the start to the inflection point, the flow velocity v depends on time t according to v = btp where b and p are empirical constants. The exponent p appears to be a nearly fundamental property of streaming onset while b is sensitive to the experimental circumstances. Important to the controversy is that the development is safely slow enough to validate Liebermann's measurement technique, typically taking two seconds to reach the inflection point and five seconds to reach 90%. of steady flow. [ABSTRACT FROM AUTHOR]

A group of hydrophone elements uniformly and closely spaced along a straight line is used to measure the angle of arrival of sound waves. By sampling the outputs of these elements rapidly and in succession, one simulates single hydrophone moving relative to the sound waves. The signal measured at the output has a frequency given by the Doppler equation f=f0(1 +α cosθ), where f0 is the frequency of the sound in the water, α is the ratio of the scanning speed to the speed of sound, and θ is the bearing angle desired. The theoretical results expected along with the experimental measurements which confirm the theory and a description of the equipment used are included. It was found that the scanned system simulates almost exactly a single moving point hydrophone, and the Doppler equation was found to hold. Pure tones and narrow-band noise signals are shifted in frequency. The angular resolution was found to be equal to the ratio of the wavelength of the sound to the component of the hydrophone length normal to the direction of sound propagation. [ABSTRACT FROM AUTHOR]

An attempt is being made to employ independent hydrophone elements uniformly spaced along a straight line to deduce the bearing of an incoming plane sound wave. Upon sampling the outputs of the hydrophone elements in succession, one simulates a single hydrophone moving relative to the sound wave. The signal measured in such a case would have a frequency of f=f0 (1 - α cosθ) where f0 is the frequency of the sound, α is the ratio of the scanning speed to the sound speed, and θ is the bearing angle to be deduced from a measurement of f. A method to accomplish this was outlined in a paper presented at the June, 1960 meeting of the Society. Since then a hydrophone about four feet long containing 134 independent elements has been obtained and the necessary switching and sampling circuits built to test the method experimentally. Measurements made in a laboratory tank confirm the theoretical results very nicely for a steady signal. These together with the results obtained using a pulsed signal and the effects of noise on the system will also be presented. [ABSTRACT FROM AUTHOR]

An attempt is being made to employ independent hydrophone elements uniformly spaced along a straight line to deduce the bearing of an incoming plane sound wave. Upon sampling the outputs of the hydrophone elements in succession, one simulates a single hydrophone moving relative to the sound wave. The signal measured in such a case would have a frequency of f = f0 (1 - α cos θ) where f0 is the frequency of the sound, α is the ratio of the scanning speed to the sound speed. and θ is the bearing angle to be deduced from a measurement of f. If two mutually orthogonal lines of hydrophones are used in the horizontal plane, the azimuth of the incoming sound wave can be determined uniquely, and the elevation angle can be found with 'up vs down' ambiguity present. Calculations show that the limit of solid angle resolution is determined by the ratio of the wavelength to hydrophone array length. The solid angle resolution is calculated from the bearing resolution Δθ = π N for a single line hydrophone where N is a number > 1. The necessary minimum number of hydrophones per unit length depends upon the arbitrary choice of α and the Shannon Sampling Theorem. The signal-to-noise ratio improves with increasing resolution, the improvement being proportional to N. [ABSTRACT FROM AUTHOR]

A systematic determination of the electromechanical coupling coefficient k has been made for Fe-Al alloys containing aluminum percentages between 12 and 14 by weight and annealed at temperatures between 600°C and 1100°C. For annealing temperatures in the neighborhood of 1000°C, k2 is about equal to 0.05 and is nearly independent of composition, a result in agreement with earlier measurements of Masumoto. For lower annealing temperatures, k2 becomes sensitive to composition, the highest value measured being equal to 0.12 for an alloy containing 12.3% Al and annealed at 650°C. In all cases eddy current losses are lower for Fe-Al than for soft annealed 'A' nickel. [ABSTRACT FROM AUTHOR]

Acetylcholinesterase inhibitors remain the mainstay of symptomatic treatment for Alzheimer's disease. The natural world is rich in acetylcholinesterase inhibitory molecules, and research efforts to identify novel leads is ongoing. Cladonia portentosa , commonly known as reindeer lichen, is an abundant lichen species found in Irish Boglands. The methanol extract of Irish C. portentosa was identified as an acetylcholinesterase inhibitory lead using qualitative TLC-bioautography in a screening program. To identify the active components, the extract was deconvoluted using a successive extraction process with hexane, ethyl acetate and methanol to isolate the active fraction. The hexane extract demonstrated the highest inhibitory activity and was selected for further phytochemical investigations. Olivetolic acid, 4- O -methylolivetolcarboxylic acid, perlatolic acid and usnic acid were isolated and characterized using ESI-MS and two-dimensional NMR techniques. LC-MS analysis also determined the presence of the additional usnic acid derivatives, placodiolic and pseudoplacodiolic acids. Assays of the isolated components confirmed that the observed anticholinesterase activity of C. portentosa can be attributed to usnic acid (25% inhibition at 125 µM) and perlatolic acid (20% inhibition at 250 µM), which were both reported inhibitors. This is the first report of isolation of olivetolic and 4- O -methylolivetolcarboxylic acids and the identification of placodiolic and pseudoplacodiolic acids from C. portentosa .

Hardware implanted during primary total joint arthroplasty carries a serious risk for periprosthetic joint infection (PJI). The formation of bacterial biofilms, which are highly tolerant of antibiotics and host immunity, is recognized as being a major barrier to treatment. It is not known whether some components and their surface features are more prone to biofilm than others. This study attempted to map biofilm on different components and features of orthopedic hardware recovered during revision. Implant surface culture (ISC) was used on 53 components from 14 hip and knee revisions. ISC achieves a thin agar coating over components, followed by incubation and observation for colony outgrowth over 9 days. Recovered organisms were identified by selective culture and 16s rRNA sequencing. Outcomes were compared with clinical culturing and PJI diagnosis based on 2013 Musculoskeletal Infection Society criteria. ISC paralleled clinical culturing with a sensitivity of 100% and a specificity of 57.1%. When compared to Musculoskeletal Infection Society criteria, sensitivity remained at 100% while specificity was 80%. Biofilm accumulation was patchy and heterogeneous throughout different prostheses, though notably the non-articulating surfaces between the tibial tray and polyethylene insert showed consistent growth. On individual components, ridges and edges consistently harbored biofilm, while growth elsewhere was case dependent. ISC successfully identified microbial growth with high sensitivity while also revealing that biofilm growth was commonly localized to particular locations. Understanding where biofilm formation occurs most often on implanted hardware will help guide debridement, retention choices, and implant design., (© 2023 The Authors. APMIS published by John Wiley & Sons Ltd on behalf of Scandinavian Societies for Pathology, Medical Microbiology and Immunology.)

The medial ankle ligamentous complex, which includes the deltoid, talocalcaneal, and calcaneonavicular ligaments, functions to provide stability to the medial ankle. Injuries to the deltoid ligament can lead to medial-sided ankle pain, subsequent instability, and posttraumatic osteoarthritis given the altered biomechanics of the ankle joint. After completing a thorough physical examination, imaging modalities such as stress radiographs and magnetic resonance imaging can be used to confirm the diagnosis. Acute injuries to the deltoid ligament should be managed conservatively with a short course of immobilization. For patients with continued pain and instability following a regimen of nonoperative management, surgical intervention can be considered. Primary repair using suture anchor fixation to the medial malleolus can be utilized if sufficient tissue remains. However, if reconstruction is necessitated, autograft or allograft can be utilized in several described techniques. Levels of Evidence: Therapeutic.

Background: Recent studies showed that healthcare disparities exist in use of and outcomes after total joint arthroplasty (TJA). This systematic review was designed to evaluate the currently available evidence regarding the effect socioeconomic factors, like income, insurance type, hospital volume, and geographic location, have on utilization of and outcomes after lower extremity arthroplasty., Methods: A comprehensive search of the literature was performed by querying the MEDLINE database using keywords such as, but not limited to, "disparities", "arthroplasty", "income", "insurance", "outcomes", and "hospital volume" in all possible combinations. Any study written in English and consisting of level of evidence I-IV published over the last 20 years was considered for inclusion. Quantitative and qualitative analyses were performed on the data., Results: A total of 44 studies that met inclusion and quality criteria were included for analysis. Hospital volume is inversely correlated with complication rate after TJA. Insurance type may not be a surrogate for socioeconomic status and, instead, represent an independent prognosticator for outcomes after TJA. Patients in the lower-income brackets may have poorer access to TJA and higher readmission risk but have equivalent outcomes after TJA compared to patients in higher income brackets. Rural patients have higher utilization of TJA compared to urban patients., Conclusion: This systematic review shows that insurance type, socioeconomic status, hospital volume, and geographic location can have significant impact on patients' access to, utilization of, and outcomes after TJA., Level of Evidence: IV., (© 2022. The Author(s).)

Background: Previous studies have shown that utilization and outcomes of total joint arthroplasty (TJA) are not equivalent across different patient cohorts. This systematic review was designed to evaluate the currently available evidence regarding the effect that patient race has, if any, on utilization and outcomes of lower-extremity arthroplasty in the United States., Methods: A literature search of the MEDLINE database was performed using keywords such as "disparities," "arthroplasty," "race," "joint replacement," "hip," "knee," "inequities," "inequalities," "health," and "outcomes" in all possible combinations. All English-language studies with a level of evidence of I through IV published over the last 20 years were considered for inclusion. Quantitative and qualitative analyses were performed on the collected data., Results: A total of 82 articles were included. There was a significantly lower utilization rate of lower-extremity TJA among Black, Hispanic, and Asian patients compared with White patients (p < 0.05). Black and Hispanic patients had lower expectations regarding postoperative outcomes and their ability to participate in various activities after surgery, and they were less likely than White patients to be familiar with the arthroplasty procedure prior to presentation to the orthopaedic surgeon (p < 0.05). Black patients had increased risks of major complications, readmissions, revisions, and discharge to institutional care after TJA compared with White patients (p < 0.05). Hispanic patients had increased risks of complications (p < 0.05) and readmissions (p < 0.0001) after TJA compared with White patients. Black and Hispanic patients reached arthroplasty with poorer preoperative functional status, and all minority patients were more likely to undergo TJA at low-quality, low-volume hospitals compared with White patients (p < 0.05)., Conclusions: This systematic review shows that lower-extremity arthroplasty utilization differs by racial/ethnic group, and that some of these differences may be partly explained by patient expectations, preferences, and cultural differences. This study also shows that outcomes after lower-extremity arthroplasty differ vastly by racial/ethnic group, and that some of these differences may be driven by differences in preoperative functional status and unequal access to care., Level of Evidence: Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence., Competing Interests: Disclosure: The Disclosure of Potential Conflicts of Interest forms are provided with the online version of the article (http://links.lww.com/JBJSREV/A816)., (Copyright © 2022 by The Journal of Bone and Joint Surgery, Incorporated.)

Celecoxib is a COX-2 inhibitor drug that can be used to reduce the risk of colorectal adenocarcinoma. Glucocorticoids are used in the treatment of inflammatory bowel disease. A limitation to the use of both drug types is that they undergo absorption from the intestinal tract with serious side effects. The prodrug systems introduced here involve forming a nitro-substituted acylsulfonamide group in the case of celecoxib and a nitro-substituted 21-ester for the glucocorticoids. Drug release is triggered by the nitro reductase action of the colonic microflora, liberating a cyclization competent species. The release of the active parent drugs was evaluated in vitro using Clostridium perfringens and epithelial transport through Caco-2 monolayer evaluation was carried out to estimate the absorption properties of the prodrugs compared to the parental drugs., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

In response to an Urgent Operational Requirement, the UK Ministry of Defence (MoD) investigated, designed, developed, trialled and subsequently fielded a Tiered Pelvic Protection System to service personnel deployed on Operation HERRICK in Afghanistan. An Urgent Statement of User Requirement (USUR) was drafted in order to equip service personnel with protection for the groin, perineum, buttocks and upper thigh areas from the effects of buried Improvised Explosive Devices (IEDs). Injuries to the groin and pelvic area from buried IEDs can have severe physiological and psychological impact; therefore the aim of the pelvic protection was to reduce the number and severity of such injuries and to improve the outcome, both in terms of quality of life of the survivors and increase the chances of survival. The aim of this paper is to outline some of the research and development that contributed to the design(s) of the Tiered Pelvic Protection System; describe the components of, and report the medical success of, the Tiered Pelvic Protection System.

Objective: Subintimal angioplasty (SA) has evolved into a viable revascularization procedure for complex lower extremity lesions. Although patency rates are lower than those for autogenous bypass, limb salvage rates are comparable. This study reviewed the 8-year experience of SA in a single center., Methods: Records of patients undergoing SA were reviewed. Clinical presentation and noninvasive exams were used to classify patients. Lesions were categorized by TransAtlantic InterSociety Consensus (TASC) II guidelines. Outcomes included technical success, patency, amputation-free survival, and limb salvage., Results: 120 patients with TASC II C/D lesions underwent SA. Technical success was 91%. Primary patency at 6 and 12 months was 90% and 73%. Secondary patency at 6 and 12 months was 94% and 85%. One-year amputation-free survival was 90%. One-year limb salvage was 98%., Conclusions: SA for TASC C/D lesions is a safe procedure and may be considered an alternative to bypass, especially in high-risk patients.

Objective: Surgical treatment of aneurysms of the anterior communicating artery complex is challenging, owing to its intricate vascular anatomy. Endoscopy is a recently rediscovered neurosurgical technique that could lend itself well to overcoming some of the vascular visualization challenges associated with this procedure. The purpose of this study was to quantify and compare the working area afforded by the microscope and the endoscope to the anterior communicating artery complex in different surgical approaches and using image guidance., Methods: We performed a total of 9 dissections, including mini-supraorbital, pterional, and orbitozygomatic approaches bilaterally in 5 whole, fresh cadaver heads. We used computed tomography-based image guidance for intraoperative navigation as well as for quantitative measurements. We estimated the working area of the anterior communicating artery complex region, using both a rigid endoscope (4.0 mm in diameter and 18 cm long with 0- and 30-degree lenses) and an operating microscope. Operability was qualitatively assessed by the senior authors., Results: In microscopic exposure, the orbitozygomatic approach provided the greatest working area (204.5 +/- 33.9 mm2), as compared with the mini-supraorbital approach (114.8 +/- 26.9 mm2) and pterional approach (170 +/- 20.4 mm2; P < 0.05). Evaluation of the endoscopic working area showed that the supraorbital approach, using both 0- and 30-degree endoscopes, provided a working area greater than that of a conventional pterional approach (P < 0.05) and comparable to that of an orbitozygomatic approach (P > 0.05)., Conclusion: In our model, use of the endoscope, in an assistive manner to microscopic surgery, provided a working area advantage without loss of microneurosurgical techniques of dissection or of depth perception in the surgical field. This advantage was most prominent when smaller craniotomies were used.

Chromatographic comparisons were made between radioactive adducts derived from the DNA of cells treated with [3H]7,12-dimethylbenz[a]anthracene and adducts derived from calf thymus DNA or nucleotides which had been treated in vitro with the synthetic syn 3,4-dihydrodiol 1,2-epoxide of this same carcinogen. This confirmed that three of the adducts formed in cells were derived from reaction of this particular dihydrodiol epoxide with deoxyadenosine while a fourth adduct was derived from its reaction with deoxyguanosine. After reaction of the dihydrodiol epoxide with polyadenylic acid, two ribonucleoside adducts were characterized by spectroscopic methods and were shown to have arisen from the cis opening of the epoxide ring at C1 by the amino group of adenine residues.

During the past decade substantial progress has been made in elucidating factors that determine the tumorigenic activity of bay-region diol epoxides, major ultimate carcinogenic metabolites derived from polycyclic aromatic hydrocarbons. Neither high nor low chemical reactivity of the diol epoxides (as measured by rates of uncatalyzed solvolysis) is required for high tumorigenic response. In contrast, aspects of molecular structure such as conformation and absolute configuration strongly influence tumorigenic activity. The role of conformation is illustrated by the observation that those diol epoxides whose hydroxyl groups are pseudoaxial are weak or inactive as tumorigens. Absolute configuration is an important determinant of biological activity of bay-region diol epoxides: in all cases studied to date, the predominantly formed (R,S)-diol-(S,R)-epoxides are generally the most tumorigenic of the four metabolically possible configurational isomers. In the course of investigating the effects of structural factors on tumorigenic activity, we identified the (4R,3S)-diol-(2S,1R)-epoxide of benzo(c)phenanthrene as the most potent tumorigen (in initiation-promotion experiments on mouse skin) of the diol epoxides studied to date. Studies of all four configurationally isomeric diol epoxides derived from benzo(c)phenanthrene led to the striking observation that these diol epoxides exhibit an exceptionally high efficiency of covalent binding, relative to hydrolysis, when allowed to react with calf thymus DNA in aqueous solution. Thus, these diol epoxides should provide an excellent tool for the detailed study of such binding. When the four isomeric benzo(c)phenanthrene diol epoxides are compared, there appears to be no simple correlation between tumorigenic response and either the extent of binding to DNA or the major types of deoxyribonucleoside adducts formed. Deoxyribonucleoside adducts of benzo(c)phenanthrene diol epoxide have also been identified from the DNA of cultured rodent embryo cells after treatment of the cells with tritium-labeled benzo(c)phenanthrene. The distribution of adducts is consistent with predominant metabolic formation of the (4R,3S)-diol-(2S,1R)-epoxide; deoxyadenosine is the major site in the cellular DNA attacked by this epoxide, just as it is in DNA in solution. Further experiments are in progress which we hope will identify more subtle aspects of the DNA binding of benzo(c)phenanthrene diol epoxides that may be uniquely correlated with their tumorigenic activity.

Since selenium has been found to exert a protective action against carcinogenesis in various systems, the mechanism where-by sodium selenite inhibits DNA binding of the carcinogen, 7,12-dimethylbenz[a]anthracene, was investigated. It was found that selenite preferentially reduced DNA binding occurring through ananti-dihydrodiol epoxide metabolite of this carcinogen by inhibiting the induction of an enzyme system that generates this specific reactive metabolite.

Four 7,12-dimethylbenz[a]anthracene--deoxyribonucleoside adducts formed in mouse epidermis in vivo arise from the syn dihydrodiol epoxide metabolite of this carcinogen. With the synthetic syn dihydrodiol epoxide it was possible to identify three of these as deoxyadenosine adducts and to establish their structures. These three adducts account for the large majority of DNA adduct arising from this metabolite in vivo. The in vivo metabolite is unusual, therefore, in that it reacts almost exclusively with adenine residues in DNA while most carcinogen metabolites react preferentially with guanine residues.

Female NIH Swiss mice were treated topically with either 0.01 or 0.1 mumol 7,12-[3H]dimethylbenz[a]anthracene and DNA was isolated either from the whole skin, the dermis or the epidermis. Levels of binding to DNA and levels of individual adducts formed were similar in all 3 tissue fractions for a given dose of carcinogen with levels for the epidermis being marginally greater than in the other fractions. In all tissue fractions, the syn dihydrodiol epoxide-deoxyribonucleoside adducts were responsible for a greater fraction of total binding at the higher, than at the lower, carcinogen dose. The mechanism of metabolic activation of 7,12-dimethylbenz[a]anthracene for DNA binding is, therefore, qualitatively the same in both the dermis and epidermis. Quantification of adducts suggests some subtle differences between the DMBA activating systems in dermis and epidermis.

In enzymatic hydrolyses of 7,12-dimethylbenz[a]anthracene (DMBA)-modified DNA isolated from fetal mouse cell cultures, a low concentration of venom phosphodiesterase was sufficient for complete release of DMBA-deoxyguanosine adducts. However, efficient release of DMBA-deoxyadenosine adducts required much higher levels of phosphodiesterase. If these adducts exhibit similarly differential susceptibilities to exonucleases involved in DNA metabolism or repair, each adduct could result in significantly different biological effects in vivo.

DNA containing bound radioactive 7,12-dimethylbenz[a]anthracene was isolated from mouse fetal cell cultures exposed to this carcinogen. The carcinogen-deoxyriboside adducts within the DNA were found to be sensitive to acid-catalyzed hydrolysis. Adducts derived from reaction of a syn-dihydrodiol epoxide with deoxyadenosine residues in DNA were the most sensitive to acid and were hydrolyzed to yield a 1,2,3,4-tetrahydrotetraol of 7,12-dimethylbenz[a]anthracene under mild conditions. The structure of this tetraol was established by synthesis and mass spectrometry. Although definitive structures cannot be assigned at present to the nucleic acid adducts of this potent carcinogen, the present findings confirm and extend earlier work assigning partial structures to the major adducts.

Primary mouse embryo cell cultures were grown in the presence of [14C]guanine, labeling primarily deoxyguanosine residues in the cellular DNA, or in the presence of [14C]adenine, labeling both deoxyguanosine and deoxyadenosine residues in the cellular DNA. These cultures were subsequently exposed to 7,12-[3H]dimethylbenz(a)anthracene for 24 hr. The DNA was isolated and hydrolyzed to deoxyribonucleosides, and the 7,12-dimethylbenz(a)anthracene:deoxyribonucleoside adducts were separated chromatographically allowing the three major adducts found to be identified as bay-region anti-dihydrodiol-epoxide:deoxyguanosine and :deoxyadenosine adducts and a bay-region syn-dihydrodiol-epoxide:deoxyadenosine adduct. Therefore, in contrast to what is known for benzo(a)pyrene, substantial amounts of deoxyadenosine adducts are formed with the more potent carcinogen, 7,12-dimethylbenz(a)anthracene.

Sodium selenite inhibits the binding of 7,12-dimethylbenz(a)anthracene (DMBA) to DNA in tertiary cultures of fetal mouse cells in a rather selective fashion. Inhibition can be demonstrated at 6 but not at 3 h after DMBA addition to the cells. Inhibition is seen after treatment of the cells with DMBA concentrations of 0.05 or 0.1 micrograms/ml but not after treatment at 0.01 micrograms/ml. Furthermore the inhibition seen with up to 1 microgram selenium/ml is selective in that products from the anti bay region dihydrodiol epoxide metabolite (where the epoxide oxygen is trans to the 4-hydroxy group) are suppressed while those from the syn-dihydrodiol-epoxide (where the epoxide oxygen is cis to the 4-hydroxy group) are not affected. In the absence of selenite, it was found that syn-dihydrodiol epoxide-DNA adducts are formed in a roughly linear fashion with time over a range of DMBA concentration. In contrast, the capacity of the cells to generate anti-dihydrodiol-epoxide adducts in a 3-h interval is saturated at concentrations of DMBA above 0.025 micrograms/ml and after the initial 3-h period the cells generate these adducts at up to a 6-fold greater rate than during the initial 3 h. This increase in rate of formation of anti-dihydrodiol-epoxide products is inhibited by actinomycin D and appears to be a consequence of DMBA inducing an enzyme activity which selectively generates the anti-dihydrodiol-epoxide and not the syn-dihydrodiol-epoxide. The selective action of sodium selenite in inhibiting only anti-dihydrodiol-epoxide product formation and doing this only at certain times and at certain doses of DMBA is a result of the fact that it inhibits the induction process. Once induction has occurred, sodium selenite is no longer inhibitory of DMBA-DNA binding. The chemopreventive action of selenium in chemical carcinogenesis could be partially attributable to effects such as those described herein on carcinogen-DNA binding. It is also possible, however, that the chemopreventive actions of selenium might be attributable to effects on the expression of genes other than those involved in carcinogen metabolism.

Primary cell cultures prepared from individual litters of NIH Swiss mouse fetuses of different gestational ages were incubated with 7,12-[3H]dimethylbenz[a]anthracene (DMBA) for 24 h. Levels of binding of DMBA to DNA and the distribution of individual DMBA-deoxyribonucleoside adducts were similar in all cultures derived from fetuses of 13-15 days of gestation. However, in cells from fetuses at 17-19 days changes in DMBA-DNA binding were noted. In particular the syn bay region dihydrodiol epoxide of DMBA was responsible for a significantly greater fraction of the total DMBA-DNA binding in the cultures from the more mature fetuses.

Compared with standard Sephadex LH-20 column chromatography, a newly developed high pressure liquid chromatographic separation of hydrocarbon deoxyribonucleoside adducts derived from the DNA of mouse embryo cell cultures exposed to 7,12-dimethylbenz[a]anthracene (DMBA) provides markedly superior resolution. Once resolved, the fluorescence spectroscopic properties of the three major DMBA--DNA adducts indicate that the fluorescence exhibited by adducts derived from a bay region syn dihydrodiol epoxide of DMBA differs subtly from that exhibited by adducts derived from the isomeric anti dihydrodiol epoxide.

Benzo(c)phenanthrene (BcPh) has only weak carcinogenic activity in rodent bioassays. However, bay-region diol-epoxides of BcPh have the highest tumor-initiating activities of all hydrocarbon diol-epoxides tested to date. To determine whether BcPh is metabolically activated to bay-region diol-epoxides that bind to DNA in cells, Sencar mouse, Syrian hamster, and Wistar rat embryo cell cultures were exposed to [5-3H]-BcPh, and the BcPh-deoxyribonucleoside adducts formed were analyzed by immobilized boronate chromatography and reverse-phase high-performance liquid chromatography. Greater than 74% of the BcPh-deoxyribonucleoside adducts formed in all 3 species resulted from reaction of (4R,3S)-dihydroxy-(2S,1R)-epoxy-1,2,3,4-tetrahydro-BcPh [(-)-BcPhDE-2] with DNA to yield deoxyadenosine and deoxyguanosine adducts in a ratio of 3:1. A much smaller proportion of BcPh-deoxyribonucleoside adducts were formed by reaction of (4S,3R)-dihydroxy-(2S,1R)-epoxy-1,2,3,4-tetrahydro-BcPh [(+)-BcPhDE-1] with deoxyadenosine. No BcPh-deoxyribonucleoside adducts arising from either (+)-BcPhDE-2 or (-)-BcPhDE-1 were detected. The absence of adducts from these isomers of BcPhDE was not due to failure of these isomers to react with DNA in cells, for reaction of (+/-)-BcPhDE-1 or (+/-)-BcPhDE-2 with DNA in solution or in hamster embryo cell cultures resulted in the formation of DNA adducts from both the (+)- and (-)-enantiomers of each BcPhDE. These results indicate that both the (+)- and (-)-3,4-dihydrodiols of BcPh are formed and that their metabolic activation to diol-epoxides occurs with high stereospecificity in cells from all 3 species of rodents. The finding that the major DNA-binding metabolite is (-)-BcPhDE-2, the diol-epoxide with the (R,S)-diol-(S,R)-epoxide absolute configuration that is associated with high carcinogenic activity of diol-epoxides of other hydrocarbons, demonstrates that these cells are able to activate BcPh to an ultimate carcinogenic metabolite. The fact that a high proportion of the BcPh-DNA adducts are deoxyadenosine adducts suggests that BcPh has DNA-binding properties similar to those of the potent carcinogen 7,12-dimethylbenz(a)anthracene. The stereospecificity observed in the metabolic activation of BcPh to DNA-binding metabolites and the reaction of these metabolites with both deoxyguanosine and deoxyadenosine suggest that studies of the interactions of BcPh with DNA in vivo may be a valuable approach for establishing the role of specific activation pathways and DNA adducts in tumor induction.

7,12-Dimethylbenz[a]anthracene (DMBA)--deoxyribonucleoside adducts formed in mouse skin DNA were quantified in order to determine whether these changed in any systematic fashion under conditions where the tumorigenic activity of DMBA is modified. Similar distributions of adducts were found in male NIH Swiss mice and C57BL mice which exhibit different sensitivities to initiation-promotion using DMBA as initiator, though in both these strains of mice the bay region syn dihydrodiol epoxide is responsible for a greater fraction of total binding at higher DMBA doses. Pretreatment with various chemicals known to inhibit the tumor initiating activity of DMBA in mouse skin did not lead to selective inhibition of the formation of any adduct in female NIH Swiss mice. However, the effects of these agents ranged from a clear inhibition of overall DNA binding (7,8-benzoflavone) to little or no effect on overall binding (butylated hydroxyanisole, butylated hydroxytoluene). The lack of any effect of the antioxidants on DMBA--DNA adduct formation suggests that they may affect some step in tumor initiation other than adduct formation.