bluuebunny/crossref_metadata_2025 huggingface dataset:
Glial Cell Line‐Derived Neurotrophic Factor: Potential for Otoprotection
Authors: KUANG R. , HEVER G. , ZAJIC G. , YAN Q. , COLLINS F. , LOUIS J.‐C. , KEITHLEY E. , MAGAL E.
Published: February 2006

ABSTRACT: Sensorineural hearing loss results from the degeneration of hair cells and/or auditory neurons in the cochlea of the inner ear. BDNF and NT‐3 were shown to support survival of auditory neurons both in vitro and in vivo. Cochlea from P3‐P4 rats were cultured as floating explants and hair cells in the organ of Corti were identified by phalloidin‐FITC immunostaining. Treatment with cisplatin (35 μg/mL) or neomycin (0.6 mM) resulted in 21.2 ± 6.0% and 7.4 ± 4.7% surviving hair cells, respectively, after 3 days in culture. GDNF, added together with the ototoxins, increased their number to 46.7% and 37.4%, respectively. In cultures of dissociated cochlea from 4‐week‐old rat, cisplatin (5 mg/mL) added 24 h after seeding resulted in only 6.1 ± 1.2% surviving neurons. However, when cisplatin was added together with GDNF (10 ng/mL), 32.8 ± 1.0% of the neurons survived. The efficacy of GDNF in animal models of ototoxicity was tested next. Guinea pigs were pretreated with GDNF in one ear, delivered either by infusion into the inner ear (scala tympani) with Alzet minipumps (50 ng/mL at a 0.5 μL/h), or injected into the middle ear (120 μL at 1 mg/mL) through the tympanic membrane. The ear that did not receive GDNF always served as control. Ototoxicity was induced systemically either by intraperitoneal cisplatin injections (1 mg/kg/day for 15 days or two injections of 7.5 mg/kg at a 5‐day interval or by a combination of kanamycin (200–300 mg/kg, administered subcutaneously) and ethacrinic acid (40 mg/kg, intravenous). It was found that the number of surviving hair cells in GDNF‐treated ears was about twice that of control ears in animals exposed to the ototoxins. The transducing GDNF receptor (ret) is expressed in the inner ear.
Role of Neurotrophins and Lectins in Prevention of Ototoxicity
Authors: GAO WEI‐QIANG
Published: February 2006

ABSTRACT: Degeneration of hair cells (HC) and/or spiral ganglion neurons (SGN) is a major cause of hearing loss. Postnatal rat cochlear explant cultures are used to study the toxic actions of different classes of ototoxins and to identify molecules that can protect SGN and HC from ototoxic damage. Various ototoxins induce differential damage to HC and/or SGN. While gentamicin preferentially causes HC death, sodium salicylate selectively induces degeneration of SGN. In contrast, cisplatin results in destruction of both SGN and HC. Specific neurotrophins, including NT‐4/5, BDNF, and NT‐3, greatly protect SGN from all three types of ototoxins. In contrast, NGF and other growth factors have no effect.

Of the 51 compounds examined, only concanavalin A (Con A), a lectin molecule, significantly protects HC from gentamicin. A dose‐dependent study of Con A shows that maximal protection occurred at 100 nM. Further experiments indicates that preincubation of Con A with gentamicin does not form a complex, and coaddition of Con A and gentamicin to bacterial cultures, such as E. Coli cultures, does not interfere with the antibiotic activity of gentamicin. When the other 21 lectins are examined, Erythrina cristagalli lectin and Detura stramonium lectin also show activity similar to Con A. These findings may help elucidate the mechanisms of ototoxins and suggest that specific neurotrophins and lectins may be of therapeutic value in the prevention of ototoxin‐induced hearing loss.
Treatment of Acoustic Trauma
Authors: D'ALDIN CHRISTINE , CHERNY LILY , DEVRIÈRE FRANCIS , DANCER A.
Published: February 2006

ABSTRACT:The aim of this study is to determine the actual efficiency of the present medical treatments of acoustic trauma. Untreated and treated groups of guinea pigs are exposed to a traumatic noise exposure, inducing up to 60‐dB threshold shift. The recovery is followed for up to 14 days. The first results indicate that in some animals the recovery of the threshold shifts are complete despite the fact that significant areas of hair cells are damaged.

The most widely used medical treatments of acoustic trauma (oxygenotherapy, carbogen, hyperbaric oxygen, vasoactive agents, and corticotherapy) have been tested. Preliminary results indicate that pure oxygen and carbogen seem ineffective, hyperbaric oxygen used alone is dangerous, and corticoids and combined corticoid/hyperbaric oxygen seem to improve functional and morphological recovery. This study will be taken as a reference to look for new treatments that will be applied directly to the cochlea by means of an implanted osmotic micropump.
Protective Effect of the Cochlear Efferent System During Noise Exposure
Authors: ATTANASIO GIUSEPPE , BARBARA MAURIZIO , BUONGIORNO GIUSEPPE , CORDIER ALDO , MAFERA BARBARA , PICCOLI FEDERICO , NOSTRO GABRIELE , FILIPO ROBERTO
Published: February 2006

ABSTRACT: The aim of the present study was to confirm the hypothesis that the cochlear efferent system is involved in the mechanisms underlying the “toughening” effect at high frequencies. The toughening effect is defined as a progressive threshold shift reduction when repeated exposures to the same noise are applied. Vestibular neurectomy was performed through a posterior cranial fossa approach in six healthy pigmented guinea pigs, and it assured the interruption of both crossed and uncrossed olivocochlear bundles to one ear only, before their entrance in the internal auditory meatus. The animals were then implanted with permanent electrodes for the electrocochleographic findings. Ten days after the operation the animals were exposed to octave‐band toughening noise, centered at 4 kHz, at 85‐dB SPL, for 10 consecutive days, 6 hours on/18 hours off. The hearing threshold was registered before and at the end of each exposure session. The behavior of the hearing threshold in the operated ears was then compared to that of the controlateral, nonoperated ears. Complete recovery from TS in the control ear began after four days of exposure, whereas in the operated ear hearing loss increased to day 7 (55 dB), with only a partial reduction (45 dB) beyond ten days of exposure.

The results of the present study clearly demonstrated that sectioning of the OCB in guinea pigs causes persistent hearing loss during noise‐exposure conditioning, in comparison to the contralateral, nonoperated ear. Thus, one can assume that the lack of decrease of TS during intermittent noise exposure could be due to the loss of the protective effect of the efferent fibers, perhaps mediated by the lateral OC neurons that synapse beneath the IHCs.
Dynamic Studies of Ototoxicity in Mature Avian Auditory Epithelium
Authors: HIROSE KEIKO , WESTRUM LESNICK E. , STONE JENNIFER S. , ZIRPEL LANCE , RUBEL EDWIN W
Published: February 2006

ABSTRACT: Hearing loss induced by ototoxicity is a worldwide problem despite the development of newer antibiotics and chemotherapy agents. The cellular mechanisms responsible for aminoglycoside‐induced hearing loss are still poorly understood. We have developed two different methods of studying the dynamic cellular and subcellular changes in the chick auditory sensory epithelium that occur during hair cell death. The first study was performed in mature chicks after a single, high dose injection of gentamicin, which results in the rapid loss of all hair cells in the basal third of the cochlea. Chicks were sacrificed at discrete time points after drug treatment, and transmission electron microscopy was performed to study the ultrastructural changes in basal hair cells during the course of cell death. We noted various changes in the cell morphology including accumulation of cytoplasmic inclusion bodies, dispersion of the cytoplasmic polyribosomes, mitochondrial swelling, and cellular extrusion by 24 h after injection. The next two studies were performed using tissue cultures from mature avian auditory sensory epithelium. Cultured cells were labeled using vital fluorescent markers, and levels of intracellular calcium and reactive oxygen species within hair cells were studied following aminoglycoside exposure. We identified a dose‐dependent increase in the levels of intracellular calcium, which was blocked by an inhibitor of voltage‐gated calcium channels. We also found that levels of reactive oxygen species in hair cells greatly increased after exposure to gentamicin, and this response was blocked by two different antioxidants. These studies serve to identify key cellular and molecular changes in hair cells in response to ototoxic drugs. Further study of these processes may lead to a better understanding of how ototoxicity is induced and to potential preventative interventions.
Intratympanic Therapy for Ménière's Disease: High‐Concentration Gentamicin with Round‐Window Protection
Authors: QUARANTA A. , ALOISI A. , DE BENEDITTIS G. , SCARINGI A.
Published: February 2006

ABSTRACT: Many therapeutic options exist for the management of patients with Ménière's disease. In the last few years, the use of intratympanic gentamicin has been investigated as an alternative treatment to vestibular nerve section or labyrinthectomy.

In humans, the concentration of gentamicin used for intratympanic treatment of vertigo ranges from 10 mg/mL to 40 mg/mL, and the number of doses from 2 to 14, with a total administered amount between 6 and 2.400 mg. Here lower doses of gentamicin were used, usually had the lowest incidence of hearing loss, but more injections were needed to ablate vestibular function.

The purpose of this study was to evaluate the acute and chronic ototoxic effects of intratympanic high‐concentration gentamicin after having obliterated the round‐window niche with connective tissue in 11 subjects' ears with Ménière's disease.

Intratympanic gentamicin was administered according to a predetermined and fixed schedule consisting of two doses of 0.5 mL gentamicin solution, injected once a week with a drug concentration of 80 mg/mL. The total dose of gentamicin was ≤80 mg.

The charts of the patients were surveyed in accordance with the 1995 AAO‐HNS guidelines. Three patients had recurrence of vertigo between 3 and 6 months after the second injection and went on to one additional dose of gentamicin.

At 2 years follow‐up, 10 patients (91%) had complete and 1 (9%) substantial control of vertigo; 3 subjects (27%) had hearing decreased. Tinnitus disappeared or decreased in 3 patients (27%); eight subjects (73%) reported their aural pressure abolished or decreased.

The present study demonstrates that in patients with Ménière's disease, 0.5 mL gentamicin solution, with a concentration of 80 mg/mL (total dose ≤80 mg), injected intratympanically once a week after having obliterated the round‐window niche, permits complete or substantial control of vertigo in two‐thirds of cases after two doses and in all subjects after three doses. This vertigo control rate is compared to that observed after vestibular nerve section. Hearing results are not different from those with natural control, with endolymphatic sac surgery, and with vestibular nerve section.
Cochlear Effects of Mesna Application into the Middle Ear
Authors: VINCENTI V. , MONDAIN M. , PASANISI E. , PIAZZA F. , PUEL J.‐L. , BACCIU S. , QUARANTA N. , UZIEL A. , ZINI C.
Published: February 2006

ABSTRACT: Mesna (sodium 2‐mercapto‐ethane sulphonate) belongs to a class of thiol compounds that produce mucolysis by disrupting the disulphide bonds of the mucus polypeptide chains. The registered indications of mesna include the treatment of pathologies of the respiratory tract and, in oncology, the prevention of toxic lesions of the urinary tract by antineoplastic agents.

In the E.N.T. Clinic of the University of Parma, it has been found that mesna can be used to facilitate the dissection of the various tissue layers in any surgical procedure. One of these indications is surgical treatment of cholesteatoma, which is mainly composed by keratin, a protein rich in disulphide bonds that are easily disrupted by mesna. The aim of this study was to evaluate the toxicity of mesna application into the middle ear on the cochlear anatomy and physiology. Three groups of guinea pigs were used as subjects. Mesna solution (10 or 20%) was applied in one ear, while the opposite ear received a placebo (saline solution). Toxicity of mesna was assessed by means of transmission electron microscopy (TEM), scanning electron microscopy (SEM), and auditory brain‐stem response (ABR). TEM and SEM did not show any toxic effect on cochlear morphology. There were no differences in ABR thresholds and wave III amplitude and latency between mesna‐treated and control ears.
The Cochleovestibular System/Ototoxicity/Clinical Issues
Authors: SHULMAN ABRAHAM
Published: February 2006

ABSTRACT: It is recommended that the experiences of basic science with ototoxicity be applied to the development of specific clinical strategies for the treatment of the cochleovestibular complaints of hearing loss, tinnitus, vertigo, and ear blockage. The treatment goals are to maintain/improve function, namely, hearing and balance, as well as to control aberrant auditory and vestibular phenomena, for example, tinnitus and vertigo originating within the peripheral and/or central cochleovestibular system.

It is hypothesized that a “common” neurochemical basis for “toxicity” exists, whatever the primary toxic etiology. It is also recommended that the neurochemical mechanisms of neuroprotection and apoptosis be considered for investigations of ototoxicity.

Furthermore, it is suggested that ototoxicities are reflected in clinical manifestations of sensory cochleovestibular complaints of hearing loss, tinnitus, and vertigo, and affect complaints of stress, pain, and neuropsychiatric disorders.
Progress in Cancer Chemoprevention
Authors: KELLOFF GARY J. , CROWELL JAMES A. , STEELE VERNON E. , LUBET RONALD A. , BOONE CHARLES W. , MALONE WINFRED A. , HAWK ERNEST T. , LIEBERMAN RONALD , LAWRENCE JULIA A. , KOPELOVICH LEVY , ALI IQBAL , VINER JAYE L. , SIGMAN CAROLINE C.
Published: February 2006

ABSTRACT More than 40 promising agents and agent combinations are being evaluated clinically as chemopreventive drugs for major cancer targets. A few have been in vanguard, large‐scale intervention trials‐for example, the studies of tamoxifen and fenretinide in breast, 13‐cis‐retinoic acid in head and neck, vitamin E and selenium in prostate, and calcium in colon. These and other agents are currently in phase II chemoprevention trials to establish the scope of their chemopreventive efficacy and to develop intermediate biomarkers as surrogate end points for cancer incidence in future studies. In this group are fenretinide, 2‐difluoromethylornithine, and oltipraz. Nonsteroidal anti‐inflammatories (NSAID) are also in this group because of their colon cancer chemopreventive effects in clinical intervention, epidemiological, and animal studies. New agents are continually considered for development as chemopreventive drugs. Preventive strategies with antiandrogens are evolving for prostate cancer. Anti‐inflammatories that selectively inhibit inducible cyclooxygenase (COX)‐2 are being investigated in colon as alternatives to the NSAID, which inhibit both COX‐1 and COX‐2 and derive their toxicity from COX‐1 inhibition. Newer retinoids with reduced toxicity, increased efficacy, or both (e.g., 9‐cis‐retinoic acid) are being investigated. Promising chemopreventive drugs are also being developed from dietary substances (e.g., green and black tea polyphenols, soy isoflavones, curcumin, phenethyl isothiocyanate, sulforaphane, lycopene, indole‐3‐carbinol, perillyl alcohol). Basic and translational research necessary to progress in chemopreventive agent development includes, for example, (1) molecular and genomic biomarkers that can be used for risk assessment and as surrogate end points in clinical studies, (2) animal carcinogenesis models that mimic human disease (including transgenic and gene knockout mice), and (3) novel agent treatment regimens (e.g., local delivery to cancer targets, agent combinations, and pharmacodynamically guided dosing).
Preclinical Mouse Models for Cancer Chemoprevention Studies
Authors: LIPKIN MARTIN , YANG KAN , EDELMANN WINFRIED , XUE LEXUN , FAN KUNHUA , RISIO MAURO , NEWMARK HAROLD , KUCHERAPATI RAJU
Published: February 2006

ABSTRACT To aid in identifying the ability of chemopreventive agents to inhibit tumor development, new preclinical in vivo rodent models have recently been developed. Some of the models contain targeted mutations capable of increasing the incidence and progression of neoplastic lesions, whereas in other models dietary nutrients induce preneoplastic lesions in normal mice. These new preclinical models are assisting the analysis of genetic and environmental factors leading to neoplasia, and clinical studies to evaluate the chemopreventive efficacy of specific nutrients and pharmacological agents.
APC and Intestinal Carcinogenesis Insights from Animal Models
Authors: BERTAGNOLLI MONICA M.
Published: February 2006

ABSTRACT The APC protein is a crucial regulator of intestinal cell growth, and mutations in the APC gene are a common initial event in the process of human colorectal carcinogenesis. animals bearing germline mutations in Apc are therefore important models for human colorectal cancer. these animals have been used both to understand the biology of human colorectal cancer and to screen for agents able to prevent malignant transformation of susceptible intestinal cells.
Cyclooxygenase‐deficient Mice: A Summary of Their Characteristics and Susceptibilities to Inflammation and Carcinogenesis
Authors: LANGENBACH ROBERT , LOFTIN CHARLES D. , LEE CHRISTOPHER , TIANO HOWARD
Published: February 2006

ABSTRACT Cyclooxygenase (COX)‐1‐ and COX‐2‐deficient mice have unique physiological differences that have allowed investigation into the individual biological roles of the COX isoforms. In the following, the phenotypes of the two COX knockout mice are summarized, and recent studies to investigate the effects of COX deficiency on inflammatory responses and cancer susceptibility are discussed. The data suggest that both isoforms have important roles in the maintenance of physiological homeostasis and that such designations as housekeeping and/or response gene may not be entirely accurate. Furthermore, data from COX‐deficient mice indicate that both isoforms can contribute to the inflammatory response and that both isoforms have significant roles in carcino‐genesis.
COX‐2 Inhibitors: A New Class of Antiangiogenic Agents
Authors: MASFERRER JAIME L. , KOKI ALANE , SEIBERT KAREN
Published: February 2006

ABSTRACT The formation of new blood vessels by angiogenesis to provide adequate blood supply is a key requirement for the growth of many tumors. While normal blood vessels expressed the COX‐1 enzyme, new angiogenic endothelial cells expressed the inducible COX‐2. We evaluated the role of COX inhibitors in the mouse corneal micropocket assay in which angiogenesis is driven by the addition of a Hydron pellet containing basic fibroblast growth factor (bFGF). Neovascular areas were measured with a slit lamp five days after pellet implantation into the corneal stroma. All animals containing implants with bFGF (90 ng) developed intensive areas of neovascularization, whereas the controls implanted with the Hydron pellet alone did not. Indomethacin (a nonselective COX‐1/COX‐2 inhibitor) and SC‐236 (a COX‐2‐selective inhibitor) inhibited angiogenesis in a dose‐dependent manner. Importantly, the indomethacin‐treated mice developed severe gastrointestinal toxicity at the efficacious dose of 3 mg/kg/day. By contrast, gastrointestinal lesions were not observed, and platelet COX‐ 1 activity was unaffected, at anti‐angiogenic doses of SC‐236 (1–6 mg/kg/day). Furthermore, a COX‐1‐selective inhibitor, SC‐560, was ineffective at doses up to 10 mg/kg, a dose that completely blocked platelet COX‐1 activity in these mice. SC‐236 was also effective in reducing angiogenesis driven by bFGF, vascular endothelium growth factor (VEGF), or carrageenan in the matrigel rat model. Finally, in several tumor models, SC‐236 consistently and effectively inhibited tumor growth and angiogenesis. This novel antiangiogenic activity of COX‐2 inhibitors indicates their potential therapeutic utility in several types of cancer.
Micronutrient Deficiencies: A Major Cause of DNA Damage
Authors: AMES BRUCE N.
Published: February 2006

ABSTRACTDeficiencies of the vitamins B12, B6, C, E, folate, or niacin, or of iron or zinc mimic radiation in damaging DNA by causing single‐ and double‐strand breaks, oxidative lesions, or both. The percentage of the population of the United States that has a low intake (<50% of the RDA) for each of these eight micronutrients ranges from 2% to 20+ percent. A level of folate deficiency causing chromosome breaks occurred in approximately 10% of the population of the United States, and in a much higher percentage of the poor. Folate deficiency causes extensive incorporation of uracil into human DNA (4 million/cell), leading to chromosomal breaks. This mechanism is the likely cause of the increased colon cancer risk associated with low folate intake. Some evidence, and mechanistic considerations, suggest that vitamin B12and B6deficiencies also cause high uracil and chromosome breaks. Micronutrient deficiency may explain, in good part, why the quarter of the population that eats the fewest fruits and vegetables (five portions a day is advised) has about double the cancer rate for most types of cancer when compared to the quarter with the highest intake. Eighty percent of American children and adolescents and 68% of adults do not eat five portions a day. Common micronutrient deficiencies are likely to damage DNA by the same mechanism as radiation and many chemicals, appear to be orders of magnitude more important, and should be compared for perspective. Remedying micronutrient deficiencies is likely to lead to a major improvement in health and an increase in longevity at low cost.
Studies of Calcium in Food Supplements in Humans
Authors: HOLT PETER R.
Published: February 2006

ABSTRACT Colon cancer is one of the commonest cancers in the Western world. Environmental factors appear to predominate as exemplified by a change in incidence in colon cancer within 20 years when people emigrate from a low‐ to a high‐incidence country. It had been suggested that a diet high in energy, fat, and meat content and low in fiber content is most likely responsible. Epidemiologic observations have pointed to a potential effect of calcium or/and vitamin D in reducing the incidence of colon cancer. other studies have shown a reduction in preneoplastic colon adenomas with increased calcium or/and vitamin D intake. high fat diets were shown to be accompanied by an increase in fecal fatty acids and bile acids or a change in bile acid composition. Soluble fatty acids and bile acids then could interact with the colonic epithelium inducing cell damage and increased proliferation. A hypothesis was developed suggesting that calcium supplementation and increased calcium in the colonic lumen would precipitate these bile acids and fatty acids. Examination of the effect of supplemental calcium or calcium in dairy foods showed a major reduction in fecal bile acids and fatty acids in solution in volunteers and accompanied by a reduction in cytolytic activity. Studies then were performed in patients at risk for colon cancer seeking a change in proliferative biomarkers of risk from a high‐risk to a low‐risk pattern with supplemental calcium administration. These studies generally have shown a beneficial effect of the addition of calcium at 1.2–2 gm per day in addition to a regular diet for periods of 2 to 6 months. A recently published study also demonstrated that a diet, in which low‐fat dairy foods containing an average of about 825 mg of calcium, significantly improved proliferative biomarkers as well as two differentiation biomarkers of risk for colon cancer from a high‐ to a low‐risk pattern. These observations, together with recent studies showing reduced adenomatous polyp recurrence when supplemental calcium was provided, demonstrate the potential of calcium and perhaps vitamin D as chemopreventive agents for colorectal neoplasia.
Calcium Supplements and Colorectal Adenomas
Authors: BARON J. A. , BEACH M. , MANDEL J. S. , van STOLK R. U. , HAILE R. W. , SANDLER R. S. , ROTHSTEIN R. , SUMMERS R. W. , SNOVER D. C. , BECK G. J. , FRANKL H. , PEARSON L. , BOND J. H. , GREENBERG E. R. ,   FOR THE POLYP PREVENTION STUDY GROUP
Published: February 2006

ABSTRACT Experimental and observational findings suggest that calcium intake may protect against colorectal neoplasia. To investigate this hypothesis, we conducted a randomized, double‐blind trial of colorectal adenoma recurrence. Nine hundred thirty patients with a recent history of colorectal adenomas were randomly given calcium carbonate (3 gm daily; 1200 mg elemental calcium) or placebo, with follow‐up colonoscopies one and four years after the qualifying examination. The main analysis focused on new adenomas found after the first follow‐up endoscopy, up to (and including) the second follow‐up examination. Risk ratios of at least one recurrent adenoma and ratios of the average numbers of adenomas were calculated as measures of calcium effect. There was a lower risk of recurrent adenomas in subjects assigned calcium. Eight hundred thirty‐two patients had two follow‐up examinations and were included in the main analysis; the adjusted risk ratio of one or more adenomas was 0.81 (95% CI 0.67 to 0.99); the adjusted ratio of the average numbers of adenomas was 0.76 (95% CI 0.60 to 0.96). Among subjects who had at least one follow‐up colonoscopy, the adjusted risk ratio of one or more recurrent adenomas was 0.85 (95% CI 0.74 to 0.98). The effect of calcium seemed independent of initial dietary fat and calcium intake. No toxicity was associated with supplementation. These findings indicate that calcium supplementation has a modest protective effect against colorectal adenomas, precursors of most colorectal cancers.
Breast Cancer Prevention by Antiestrogens
Authors: OSBORNE MICHAEL P.
Published: February 2006

ABSTRACT A new era has been entered with the first demonstration that an antiestrogen can prevent breast cancer. in a landmark study tamoxifen was shown to reduce the incidence of breast cancer by ∼50%. The reduction was observed in pre‐ and postmenopausal women at increased risk of breast cancer. Invasive cancers were reduced, the reduction being in the estrogen receptor‐positive cancers. No preventive effect was observed for estrogen receptor‐negative tumors. In situ cancers were also significantly reduced. A collateral benefit was a significant reduction in fractures due to osteoporosis. Adverse effects included a very small increase in the incidence of endometrial cancer, cataracts, and stroke. The benefits appear to outweigh the risks for those at high risk. Preliminary studies of a new selective estrogen receptor modulator (SERM 2), raloxifene, developed for the prevention of osteoporosis, have shown that the breast cancer rate was reduced by more than 50% without any concomitant increase in endometrial cancer. the search for a SERM 3, and beyond, may lead to the development of drugs that have the beneficial effects of estrogen while preventing breast cancer and osteoporosis.
Squalene, Olive Oil, and Cancer Risk: Review and Hypothesis
Authors: NEWMARK HAROLD L.
Published: February 2006

ABSTRACT Epidemiologic studies of breast and pancreatic cancer in several Mediterranean populations have demonstrated that increased dietary intake of olive oil is associated with a small decreased risk, or no increased risk, of cancer, despite a high overall lipid intake. Experimental animal models in high dietary fat and cancer also indicate that olive oil either has no effect, or a protective effect, on the prevention of a variety of chemically induced tumors. As a working hypothesis, it is proposed that the high squalene content of olive oil, as compared to other human foods, is a major factor in the cancer‐risk reducing effect of olive oil. Experiments in animal models suggest a tumor‐inhibiting role for squalene. A mechanism is proposed for the tumor‐inhibitory activity of squalene based on its known strong inhibitory activity of HMG‐COA reductase catalytic activity in vivo, thus reducing farnesyl pyrophosphate (FPP) availability for “prenylation” of ras oncogene, which relocates this oncogene to cell membranes and is required for the signal‐transducing function of ras. Reduction of mutated ras oncogene activation may be useful in breast and colon cancer and may be particularly applicable to pancreatic cancers that are strongly associated with ras oncogenes.
Electrode Phenomena in Plasma Torches
Authors: HEBERLEIN JOACHIM
Published: February 2006

ABSTRACT: The performance of most plasma generators using electric arcs is determined by the design of the electrodes. While the cathode design is the dominant factor in determining the limitations in torch operating current and power level as well as life between maintenance, the anode design dominates the functional performance for most torches, i.e. the heat and momentum transfer to the materials to be processed. Plasma torch electrodes are conveniently divided into the following categories: (1) thermionic cathode, (2) non‐thermionic (cold) cathode, (3) anode with arc axis and flow perpendicular to the surface, and (4) anode with the arc axis and the flow parallel to the surface. All possible combinations are encountered in commercially available torches. In this review, the performance characteristics of each of these electrode types are discussed.
A Non‐equilibrium Treatment for Free Burning High Current Arcs.
Authors: HAIDAR J.
Published: February 2006

ABSTRACT: A two‐temperature variable‐density treatment has been developed for description of high current free burning arcs, including departures from thermodynamic and chemical equilibrium in the plasma. The treatment includes the arc and the electrodes, and considers the separate energy balance of the electrons and the heavy particles, together with the continuity equations for these species throughout the plasma. For a 200 A arc in pure argon at 1 atm, we calculate large differences between the temperatures of the electrons and the heavy particles in the plasma region near the cathode tip. In the main body of the arc, at high plasma temperatures, we predict minor differences between the temperatures of the electrons and the heavy particles. However, we predict large departures from local chemical equilibrium throughout the plasma, due to overpopulation of the ground state level of the neutral atoms caused by the injection into the arc core of a large mass flow of cold gas, resulting from the arc constriction at the tip of the cathode.
Erosion of the Cold Electrode as an Ablation Process in Unsteady Arc Spotsa
Authors: MAROTTA ARUY , SHARAKHOVSKY LEONID I. , ESSIPTCHOUK ALEXEI M.
Published: February 2006

ABSTRACT: A simple macroscopic thermophysical model is presented for cold electrode erosion in unsteady arc spots. The model is based on the consideration of erosion as heat ablation characterized by an effective enthalpy of erosion of the electrode material. The unbalance between the arc spot heat supply and the heat removal by conduction into the electrode body provides the heat spent in the erosion process. Two modes of displacement of the arc spot are considered: continuous and step‐wise. An experimental coaxial setup with a magnetically driven arc has been used for conducting erosion measurements in copper cathodes. Good agreement between this experiment and those reported by other researchers has been obtained with the continuous and the step‐wise models. Electrical Discharge Machining experimental data in steel cathodes have also shown good agreement with our step‐wise erosion model.
Water vapour Plasma Torch for Hazardous Waste Treatment
Authors: KEZELIS ROMUALDAS , JUSKEVICIUS ROMUALDAS , MECIUS VLADAS
Published: February 2006

ABSTRACT: Voltage‐current and thermal characteristics of a water vapour plasma torch are described. Experiments were performed at arc power
N = 6–20 kW

, current
I = 30–180 A

, voltage
U = 90–240 V
. Water vapour jet temperature as a function of flow rate of water vapour and current is presented.
Effect of Vortex Motion of Stabilizing Liquid Wall on Properties of Arc in Water Plasma Torcha
Authors: JENIŠTA JIŘÍ , HRABOVSKÝ MILAN , KOPECKÝ VLADIMÍR
Published: February 2006

ABSTRACT: In water stabilized plasma torches an electric arc is ignited in a centre of water vortex which is created in cylindrical arc chamber with tangential water injection. The arc is stabilized by an interaction with inner wall of the vortex. Principle physical mechanisms which control arc properties and parameters of generated plasma jet are evaporation of water wall and heating and ionization of vapour flowing from the wall into the arc column. The vortex movement of water is necessary to maintain fixed shape of inner wall of the vortex due to inertial forces. Published model of mechanisms of water stabilized arc does not consider effect of movement of water on mechanisms of arc 1. The aim of investigation described in this paper is theoretical and experimental study of the effect of movement of water and induced tangential component of velocity of plasma in the arc column on properties of arc and generated plasma jet.
Plasma Concentrations out of Equilibrium: N2 (Kinetic Method and Mass Action Law), Ar‐CCl4 and Ar‐H2‐CCl4 (Mass Action Law)
Authors: ANDRE PASCAL , AUBRETON JACQUES , ELCHINGER MARIE‐FRANCOISE , FAUCHAIS PIERRE , LEFORT ANDRE
Published: February 2006

ABSTRACT: The multi‐temperature Gibbs free energy minimization (GFEM) method has been compared to the Pseudo Kinetic Method (PKM) to calculate the composition of a nitrogen plasma at atmospheric pressure. When introducing only two temperatures Te and Th with their ratio
θe= 2

, the GFEM method overestimates by more than two orders of magnitude the density of N2+. However when calculating the kinetic rate coefficient at different temperatures the thermodynamic relationship between them and the equilibrium constant is no more fulfilled. That is why an intermediate temperature T* between Te and Th has been introduced linked to the ratio of the electrons flux to that of neutrals and θe has been assumed to vary with the electron density ne, equilibrium (
θe= 1

) being achieved either for
nemax= 1022 or 1023 m−3

. With n
emax= 1022 m−3

the agreement between the results obtained with the PKM and the GFEM method is fairly good. That is why this latter method has been used to calculate the composition of complex mixtures of Ar‐CCl4 and Ar‐H2‐CCl4. Below 6000 K where complex molecules exist the variation of θe between 2.5 and 1.5 does not affect very much the composition which, however, depends strongly on θv (
θv= Tv/Th
)
Analysis and Modeling of Decontamination Experiments of Depleted Uranium Dioxide in RF Plasma
Authors: EL‐GENK MOHAMED S. , SABER HAMED H. , VEILLEUX JOHN
Published: February 2006

ABSTRACT: Analysis was performed of the results of UO2 etching experiments, which used NF3 RF glow discharge. In the experiments, the gas pressure was varied from ∼10 ‐ 40 Pa and the absorbed power was varied from 24 ‐ 210 W. The UO2 etch reactions to form volatile UF6 were strongly dependent on the absorbed power and, to a lesser extent, on pressure. At and below 50 W absorbed power, UO2 etching increased with pressure up to ∼ 23 Pa, then decreased with further increase in pressure. At higher power, however, UO2 etching increased monotonically with pressure. The UO2 etching process was self‐limiting, due to the formation of non‐volatile products UF2–5, UO2F, and UO2F2. The accumulation of UF6 and O2 in the plasma sheath also reduced the diffusion coefficient of atomic fluorine radicals to the UO2 surface thereby contributing to the decrease in etch rate with immersion time.
Application of the Dielectric Barrier Discharge Jet in Surface Treatment and Film Depositiona
Authors: NUTSCH G. , NOLIN S. , HEIDER TH. , ROTHER W.
Published: February 2006

ABSTRACT: This paper presents the application of a special dielectric barrier discharge for surface treatment and deposition of 3D work pieces. Similar to a plasma jet generation for plasma spraying the DBD jet is generated by a gas flow of a high gas flow rate which is activated by the barrier discharge inside the torch and leaves the nozzle with a high velocity. The reactive potential of this exiting jet was measured by electrical probe measurements as a function of the sustaining power level, the flow rate of the working gas and the distance from the nozzle. There is a strong relation between the probe current and the surface tension. The DBD Jet is also tested for application of thin film deposition using acetylene as process gas.
Diagnostics and Modelling of a Thermal RF Plasma Process Used for the Flash Evaporation of Zirconia Powders
Authors: Buchner P. , Schubert H. , Uhlenbusch J. , Weiβ M. , Willée K.
Published: February 2006

ABSTRACT: The evaporation process of zirconia powders injected in a thermal RF plasma is investigated. Both model calculations and experimental techniques such as Optical Emission Spectroscopy (OES) and Laser Doppler Anemometry (LDA) are used to study the evaporation behaviour. Gas temperatures and velocity distributions are determined numerically from conservation laws and Maxwell equations. The influence of plasma and particle parameters on the thermal interaction of injected particles is discussed. Asymmetric Abel inversion is applied to detect asymmetric emission profiles in the plasma source. Spectroscopic measurements reveal that evaporated zirconia is concentrated near the axis of the plasma. Numerical calculations show that line‐integrated emission profiles can be used to distinguish the cases of complete and incomplete evaporation.

LDA measurements of the particle velocity distribution show good agreement with the results achieved with modelling.
Non‐Equilibrium Effects in Gliding Arc Dischargesa
Authors: MUTAF‐YARDIMCI OZLEM , SAVELIEV ALEXEI V. , PORSHNEV PETR I. , FRIDMAN ALEXANDER A. , KENNEDY LAWRENCE A.
Published: February 2006

ABSTRACT: The properties of the non‐equilibrium Gliding Arc plasma were studied both experimentally and theoretically. The propagation of the plasma column was recorded continuously by using a high‐speed video camera. A theoretical model was developed to determine the characteristics of the equilibrium‐nonequilibrium transition. The transition is explained by the drastic change of the dominant ionization channel when the contribution of the thermal ionization to the electron density balance becomes less important than that of the direct electron impact ionization. According to our theoretical model, the majority of the Gliding Arc power (up to 75–80%) can be dissipated in the cold non‐equilibrium stage. Powerful non‐equilibrium plasma can be generated from the initially thermal Gliding Arc discharge.
NUMERICAL MODELLING OF ELECTRODE PLASMA GENERATION
Authors: NG W. L. , TUTTY O. R. , MCBRIDE J. W.
Published: February 2006

ABSTRACT: A numerical scheme for a multi‐species, non‐equilibrium reacting, viscous gas flow is presented here. The code has been used for a simplified model of the plasma flow under the electrical arcing condition. Initially the gas is pure molecular Nitrogen N2 and the plasma is initiated by electron emission from the cathode wall.
Interaction of Weakly Ionized Highly Dissociated Hydrogen Plasma with Solid Surfacesa
Authors: MOZETIČ MIRAN
Published: February 2006

ABSTRACT: Experimental study of the physical and chemical interaction of hydrogen plasma with a variety of samples is described. Hydrogen plasma was created by the use of an inductively coupled RF generator with the output power from 100 up to 300 W. Plasma parameters were measured with electrical and catalytic probes. At the pressure between 5 and 500 Pa the electron temperature was about 6 eV, plasma density of the order of 1015 m−3 and degree of dissociation about 10%. Recombination of neutral hydrogen atoms on different metals and alloys was studied. For the case of pure nickel the recombination coefficient was constant while for inconel it was a complex function of the temperature. Discharge cleaning experiments were performed on samples of contact materials, archeological artifacts and chip bases. The cleanliness of the surface was monitored with AES depth profiling and EMPA method. In any case, the layer of impurities was effectively removed from the sample surfaces by exposure to hydrogen plasma.
NONLINEAR CONVECTIVE HEAT TRANSFER IN A TRANSITIONAL PLASMA PLUMEb
Authors: KREJČÍ LUDĚK , DOLÍNEK VLADIMÍR , SOPUCH PAVEL , NĚNIČKA VÁCLAV , HLÍNA JAN
Published: February 2006

ABSTRACT: In the paper the results of experimental investigation of wave‐like heat transfer events taking place in the core of transitional plasma plumes are presented and discussed. In order to amplify the dynamic events governing them the arc heater operating conditions were chosen in such a manner that the strong feedback in the plasma column predominated during the nonlinear phase of the transition process. This enabled us to state, that in the events studied the crucial role plays an unstable plume shear layer vortex system inducing the oscillations of the whole plasma column. And just the coupling of them with a mode of organ pipe acoustical oscillations in the arc chamber cavity results in self sustained oscillations of the column and in strong linkage between the thermal events taking place in the plume and the arc chamber cavity. However, the results gained allow us not only to grasp the mechanism of the heat transfer process in the plume core during the transition to turbulence but also provide a means for formulating a conceptual model (scenario) of its evolution. And on the basis of this piece of knowledge a theoretical approach based on the methods of the nonlinear dynamics theory is proposed.
Numerical Simulation of Multi‐Component Inductive Plasma Flows under Chemical Non‐Equilibrium
Authors: VANDEN ABEELE DAVID , BARBANTE PAOLO , DEGREZ GERÁRD , GONZÁLEZ JUAN‐PEDRO MELLADO
Published: February 2006

ABSTRACT: This contribution presents an elegant and efficient numerical model of a multi‐component inductive plasma under chemical non‐equilibrium. The plasma is modeled by a finite number of species. Chemical reactions are taken into account by Arrhenius‐type source terms. The plasma thermodynamic properties are computed from statistical mechanics. The plasma transport properties are computed with the method of Chapman and Enskog. Multi‐component species diffusive fluxes are obtained from the full Stefan‐Maxwell equations by means of a straightforward iterative procedure, in which no distinction needs to be made between electrons and heavy particles. The governing equations are discretized in a second order accurate cell‐centered finite volume manner on a collocated mesh. The discretized system of equations is solved with a damped Newton method. Powerful Krylov subspace methods are used to efficiently solve the linear systems arising from the Newton linearization. Results are presented for a five‐species nitrogen plasma. The effect of chemical non‐equilibrium is investigated at various pressures. Though some problems still need to be addressed, good convergence is already found. Calculations of eleven‐species air plasmas under thermochemical non‐equilibrium seem feasible for the near future.
Transport of neutral atomic hydrogen in a supersonic plasma jet.
Authors: Mazouffre S. , Boogaarts M.G. H. , van Der Mullen J.A. M. , Schram D. C.
Published: February 2006

ABSTRACT: In a supersonically expanding plasma jet created by a cascaded arc from an Ar‐H2 mixture, spatially resolved densities, temperatures, and velocities of ground state atomic hydrogen are obtained by applying two‐photon excitation laser induced fluorescence. The axial velocity profile of H indicates a strong coupling between Ar and H atoms and it can be fully described in terms of a supersonic expansion model. However, whereas H atoms temperature profiles along the jet centerline clearly reveal the presence of a normal shock front, the atomic hydrogen density profiles do not. From the absence of a density jump across the normal shock front, it is conclude that the atomic hydrogen flux in the axial direction is not conserved. There are several indications that the coupling between H and Ar atoms is lost in the course of the expansion and that hydrogen atoms can escape the supersonic domain by a scattering process due to their large mean free path.
Study of High Enthalpy Plasma Flows
Authors: BELEVTSEV ANDREI A. , GRIGOR'YANTS RUBEN R. , ISAKAEV EMIN KH. , IVANOV PETER P. , MARKIN ALEXANDER V. , CHINNOV VALERY F.
Published: February 2006

ABSTRACT: The paper deals with spectroscopic studies on high enthalpy atmospheric pressure plasma flows generated with a divergent channel arc plasmatron, the line along which an essential progress has recently been made in Associated Institute for High Temperatures of the Russian Academy of Science. Argon and nitrogen are chosen as working media because they offer significant technological merits over most other gases. The spectra have been taken in the 200–950nm region with a high spectral resolution of∼0.01–0.02nm. Their evolution along the jet is investigated in combination with determining radial distributions of irradiating components through the Abel inversion. For extracting and processing a large amount of spectrometric information in a reasonable time, a purpose‐developed automated measuring system is employed. Described are the main basic principles and how the system works. Particular attention is given to spectrally determining the influence of a gas flow rate on the plasma parameters. Some possible mechanisms resulting in charged species formation in the far plasma relaxation zone where no electric fields and currents exist are briefly touched on.
Comparison of Experimental and Numerical Results for the Dynamic Pressure in an Inductive Plasma Flow
Authors: CHAZOT OLIVIER , VANDEN ABEELE DAVID , CARBONARO MARIO
Published: February 2006

ABSTRACT: Plasmatron facilities are designed for Thermal Protection System (TPS) testing of re‐entry vehicles. These tests require plasma flow characterization with specific measurement techniques. In this aim, numerical code results and Pitot probe measurements are compared and presented. Such a comparison permits validation of the code from experimental measurements and facilitating the interpretation of the measured Pitot results. It allows as well the examination of the behavior of a cooled Pitot probe in plasma flow condition
Numerical and Experimental Study of Microscopic Particles Distribution Under Corona Discharge: Case of Wire‐Cylinder Electrostatic Precipitator
Authors: SEMMAR NADJIB , KHALIJ MOHAMED , RIGO MARIE‐ODILE
Published: February 2006

ABSTRACT: The behaviour of microscopic particles under a corona discharge is studied in this paper. The convection‐diffusion equation is resolved in the case of wire‐cylinder electrodes by a finite differences method. Selection of this configuration allows to eliminate the complex EHD interactions observed in the case of wire‐plate electrostatic precipitators. Otherwise, particle size measurements are realised in a lab‐scale electrostatic precipitator for atmospheric aerosols. Their linear distribution is consequently verified over the range [0.5 ‐ 2.0 μm]. In other words, particle‐particle, wall‐particle interactions and coalescence phenomena might be reasonably neglected in the case of dilute gas flows under strong electric fields.