Male Reproductive Assessment of the Rubber Accelerator N-Oxydiethylene Thiocarbamyl-N-Oxydiethylene Sulfenamide in Rats

The rubber accelerator N-oxydiethylene thiocarbamyl-N-oxydiethylenesulfenamide (OTOS) was evaluated to determine its potentialto cause reproductive effects. No evidence of a compound-relatedeffect on mating, fertility, gestation length, number of implantsor live births, pup growth, and survival was observed usingSprague–Dawley rats. Furthermore, light and electron microscopyof the testes from the high-dose males failed to reveal anymorphological changes compared to the controls. Groups of 12male Sprague–Dawley rats were continuously administereddiets containing 0, 60, 200, or 600 ppm OTOS for 12 weeks. Following56 days of exposure, the males were subsequently cohoused nightlywith two females for a maximum of 21 days. During this matingperiod, males continued to receive control and OTOS-containingdiets; however, feeders were removed for nightly cohabitation.Although a 4 to 8% reduction in body weight was observed inthe 600 ppm animals, statistical significance was reached onlyat the end of the first week of treatment. In the 60 and 200ppm males body weights generally were slightly elevated comparedto the control, with the 60 ppm body weights showing statisticallysignificant differences during Weeks 5 to 7 of exposure.     

A Quantitative Approach for Benefit-Risk Assessment Using Stochastic Multi-Criteria Discriminatory Method

ABSTRACT

Benefit-risk (BR) assessment is important to ensure safety and effectiveness of medical projects in clinical development and post marketing surveillance. The evaluation of the balance between benefits and risks of a drug is fundamental to all stakeholders involved in the development, registration, and use of drugs. Many quantitative approaches have been developed that may draw together data from different sources to present them in ways that can aid decision-making. Among these quantitative approaches, multicriteria decision analysis (MCDA) is one of the most useful approaches, since it provides a framework for systematic and replicable analyses of complex decision problems involving value tradeoffs. In most real-life situations, decision makers are not able to get exact preference information (weights). To overcome this limitation of MCDA, a method called stochastic multicriteria acceptability analysis (SMAA) was proposed as a quantitative approach to BR assessment in drug development. The chief advantage of SMAA over most other MCDA methodologies is that it can be used with limited or no preference information and a data-driven approach can be used to obtain the inherent weighting among multicriteria. In this article, we propose the stochastic multicriteria discriminatory method (SMDM) that is based on the SMAA method with a focus on providing straightforward and informative assistance to decision making. We use SMDM to derive probability of better treatment, probability of significantly better treatment and the expected p-values of the evaluation results, on the basis of limited partial weight information or no weight information at all.     

A Review of the Endocrine Activity of Parabens and Implications for Potential Risks to Human Health

Parabens are a group of the alkyl esters of p-hydroxybenzoic acid and typically include methylparaben, ethylparaben, propylparaben, butylparaben, isobutylparaben, isopropylparaben, and benzylparaben. Parabens (or their salts) are widely used as preservatives in cosmetics, toiletries, and pharmaceuticals due to their relatively low toxicity profile and a long history of safe use. Testing of parabens has revealed to varying degrees that individual paraben compounds have weakly estrogenic activity in some in vitro screening tests, such as ligand binding to the estrogen receptor, regulation of CAT gene expression, and proliferation of MCF-7 cells. Reported in vivo effects include increased uterine weight (i.e., butyl-, isobutyl-, and benzylparaben) and male reproductive-tract effects (i.e., butyl- and propylparaben). However, in relation to estrogen as a control during in vivo studies, the parabens with activity are many orders of magnitude less active than estrogen. While exposure to sufficient doses of exogenous estrogen can increase the risk of certain adverse effects, the presumption that similar risks might also result from exposure to endocrine-active chemicals (EACs) with far weaker activity is still speculative. In assessing the likelihood that exposure to weakly active EACs might be etiologically associated with adverse effects due to an endocrine-mediated mode of action, it is paramount to consider both the doses and the potency of such compounds in comparison with estrogen. In this review, a comparative approach involving both dose and potency is used to assess whether in utero or adult exposure to parabens might be associated with adverse effects mediated via an estrogen-modulating mode of action. In utilizing this approach, the paraben doses required to produce estrogenic effects in vivo are compared with the doses of either 17β-estradiol or diethylstilbestrol (DES) that are well established in their ability to affect endocrine activity. Where possible and appropriate, emphasis is placed on direct comparisons with human data with either 17β-estradiol or DES, since this does not require extrapolation from animal data with the uncertainties inherent in such comparisons. Based on these comparisons using worst-case assumptions pertaining to total daily exposures to parabens and dose/potency comparisons with both human and animal no-observed-effect levels (NOELs) and lowest-observed-effect levels (LOELs) for estrogen or DES, it is biologically implausible that parabens could increase the risk of any estrogen-mediated endpoint, including effects on the male reproductive tract or breast cancer. Additional analysis based on the concept of a hygiene-based margin of safety (HBMOS), a comparative approach for assessing the estrogen activities of weakly active EACs, demonstrates that worst-case daily exposure to parabens would present substantially less risk relative to exposure to naturally occurring EACs in the diet such as the phytoestrogen daidzein.     

Developmental Exposure to Tetrabromobisphenol A Has Minimal Impact on Male Rat Reproductive Health

The flame retardant and plasticizer, tetrabromobisphenol-A (TBBPA) has rapidly become a common component in the manufacture of circuit boards and plastics worldwide. It is also an analog of bisphenol A (BPA), an endocrine disrupting chemical identified by the Endocrine Society. As such, TBBPA needs to be investigated for similar potential human health risks. Using rats as a model, we exposed pregnant dams and their progeny to 0, 0.1, 25, or 250 mg TBBPA/kg of body weight until the offspring reached adulthood and assessed the first generation of males for any reproductive tract abnormalities. We found no differences in the morphology of testes, sperm, prostates, or secondary sex organs from post-natal day 21 through one-year of age. A delay in the time to preputial separation was found with the 250 mg/kg treatment. Also, minor differences of sperm count at one-year old with the 25 mg/kg treatment and expression levels of two steroidogenic pathway enzymes at either post-natal day 90 or one-year old in the 250 mg/kg treatment group were detected, but spermatogenesis was not disrupted. While these results may lead to the supposition that TBBPA is less harmful than its parent compound BPA, more studies need to be conducted to assess long-term exposure effects.     

Assessment of the Reproductive Toxic Potential of Dermally Applied 2-Hydroxy-4-methoxybenzophenone to Male B6C3F1 Mice

The potential of 2-hydroxy-4-methoxybenzophenone (HMB) to causemale reproductive toxicity was assessed in B6C3F1 mice. HMBwas administered topically for 13 weeks (5 days/week) to groupsof 10 mice each at dosages of 0, 10, 20, 100, or 400 mg/kg/day.Additional high dosage and control mice were also included andeuthanized at interim time points to characterize the time courseof any effects. After 91 days (or at interim periods) mice wereeuthanized and reproductive organ weights, cauda epididymalsperm concentration and proportion of motile and abnormal sperm,and testicular spermatid concentration were determined. Testicularhistology was evaluated in fixed tissue. HMB treatment had noeffect on body weight gain or any of the male reproductive parametersassessed at any time point. These results indicate that topicallyapplied HMB has no reproductive toxic potential in male B6C3F1mice at dosages as high as 400 mg/kg/day.     

Lack of Reproductive Toxicity in Adult Male Rats Exposed to Interferon-Alpha

Interferon-alpha (IFN-α), a type I IFN, is a protein with antiviral, antiproliferative, and immunoregulatory activities, widely used in the treatment of several types of cancers as well as hepatitis B and C. Decrease of libido and erectile dysfunction are commonly reported by male patients during treatment of chronic hepatitis C with IFN-α. However, IFN therapy-associated underlying factors attributed to sexual dysfunction are still not well defined. Currently, there are few studies investigating the effects of IFN on male reproductive system functions. Given that, the aim of the present investigation was to examine effects of subchronic exposure to IFN-α (5 × 10⁴ U/kg and 10 × 10⁴ U/kg, 30 d) on serum hormones, sperm parameters, fertility, and testicular and epididymal hystopathology and morphometry in adult male Wistar rats. None of the evaluated parameters was markedly altered by IFN-α. Thus, our results suggest that exposure to IFN-α, in this experimental design, did not adversely affect sperm quality and fertile capacity of male rats.     

Studies on the Male Reproductive Toxicity of Freon 22

Studies on the Male Reproductive Toxicity of Freon 22. Lee,I.P. and Suzuki, K. (1981). Fundam. Appl. Toxicol. 1:266–270Freons have been used extensively as refrigerants and as propellantsin household products, and yet their possible effects on malereproduction have received little attention. In the presentstudy, adult male Sprague-Dawley rats (nine weeks of age) wereexposed to 50 000 ppm Freon 22, five hrs per day for eight weeks.The control group received filtered air at an identical flowrate. At the end of the eight week exposure period, body andorgan weights, hematology, blood chemistry, plasma gonadotropins,and fertility parameters were not significantly different fromcontrols, with the exception of serum cholesterol levels, whichwere slightly higher, and glucose and triglyceride levels whichwere lower. The weight of coagulating glands was also lowerthan those of controls, but did not interfere with fertilityfunction.     

Reproductive Toxicology of Aluminum in Male Mice

The reproductive toxicology of aluminum was studied in mice.Adult male mice were treated intraperitoneally with aluminumnitrate at doses of 0, 50, 100, and 200 mg/kg/day for 4 weeksbefore mating with untreated females. Decreased body weightwas seen in all aluminum-treated groups. Decreased pregnancyrate was observed in the females mated with males previouslytreated with 100 or 200 mg/kg/day of aluminum nitrate. High-dosemale mice showed significantly decreased testicular and epididymalweights, as well as significant decreases in testicular andspermatid counts and epididymal sperm counts. Spermatid countswere also reduced at 100 mg/kg/day. However, the sperm motilitywas unaffected, and the percentages of morphological normalspermatozoa in all mice exposed to aluminum were comparableto the values in control mice. Histological changes, includingnecrosis of spermatocytes/spermatids, were observed in the testesof male mice treated with 100 and 200 mg/kg/day of aluminumnitrate, whereas the tubu lar diameters were unaffected by aluminumadministration. The current study demonstrates adverse effectsof parenteral aluminum exposure on the mouse male reproductivesystem. The "no observable adverse effect level" (NOAEL) was50 mg/kg/day.     

A Quantitative Disintegration Method for Polymeric Films

Purpose

Current in vitro disintegration methods for polymeric films are qualitative and introduce significant user bias. The goal of these studies is to develop a novel, quantitative disintegration technique which can be used to characterize polymeric films in vitro.

Methods

A method was developed using a Texture Analyzer instrument to evaluate film disintegration. Solvent-casted, clinically advanced, anti-HIV, vaginal films as well as marketed vaginal films were used throughout these studies. Method development followed a quality by design (QbD) process and was used to evaluate film products.

Results

The current method developed provided reproducible, quantitative disintegration times for the commercially available vaginal contraceptive film (57.88?±?5.98 s). It distinguished between two clinically advanced antiretroviral containing films based on disintegration time (p value <?0.001): the tenofovir film (41.28?±?3.35 s) and the dapivirine film (88.36?±?10.61 s). This method could also distinguish between tenofovir and dapivirine films which had been altered in terms of volume (p?<?0.0001) and formulation (p?<?0.0001) based on disintegration time.

Conclusions

This method can be applied for pharmaceutical films for ranging indications as part of vigorous in vitro characterization. Parameters of the test can be altered based on site of application or indication.

     

Assessment Factors for Human Health Risk Assessment: A Discussion Paper

The general goal of this discussion paper is to contribute toward the further harmonization of human health risk assessment. It first discusses the development of a formal, harmonized set of assessment factors. The status quo with regard to assessment factors is reviewed, that is, the type of factors to be identified, the range of values assigned, as well as the presence or absence of a scientific basis for these values. Options are presented for a set of default values and probabilistic distributions for assessment factors based on the state of the art. Methods of combining default values or probabilistic distributions of assessment factors are also described. Second, the effect parameter, the no-observed-adverse-effect level (NOAEL), is discussed. This NOAEL as selected from the toxicological database may be a poor substitute for the unknown, true no-adverse-effect level (NAEL). New developments are presented with respect to the estimation of the NAEL. The already widely discussed Benchmark Dose concept can be extended to obtain an uncertainty distribution of the Critical Effect Dose (CED). This CED distribution can be combined with estimated uncertainty distributions for assessment factors. In this way the full distribution of the Human Limit Value will be derived and not only a point estimate, whereas information on dose-response relations is taken into account. Finally, a strategy is proposed for implementation of the new developments into human health risk assessments.     

Adverse Male Reproductive Effects following Subchronic Exposure of Rats to Sodium Dichloroacetate

Dichloroacetate (DCA) activates the pyruvate dehydrogenase complexenhancing carbohydrate and lactate utilization in animals. Asa result it is used clinically in the treatment of acute lacticacidosis and has therapeutic potential in the treatment of stroke.Adverse effects of chronic DCA treatment include poly-neuropathyand testicular degeneration. Since DCA is a principal productof the aqueous chlorination of fulvic acids concern has arisenregarding the agent's impact on environmental health. We treatedmale Long-Evans rats with 0, 31.25, 62.5, or 125 mg DCA/kg/dayby oral gavage for 10 weeks. Compared to controls, preputialgland and epididymis weights were reduced at 31.25 mg/kg, bodyand liver weights at 62.5 mg/kg, and accessory organ weightsat 125 mg/kg. Epididymal sperm counts were reduced and spermmorphology was impacted at the 62.5 and 125 mg/kg doses levels.Histologic examination of the testis and epididymis revealedinhibited spermiation in testes at the 125 mg/kg dose level.Computer-assisted sperm motion analysis revealed reductionsin percentage motile sperm, curvilinear and straight-line velocity,linearity, and amplitude of lateral head displacement at boththe 62.5 and the 125 mg/kg dose levels. In the assessment offertility after an overnight mating, the number of viable implantson Day 14 of gestation was decreased only in the highest dosegroup. These studies demonstrate adverse effects of NaDCA treatmenton the rat male reproductive system, primarily on the accessoryorgans and sperm within them at lower doses (31.25 and 62.5mg/kg), and on the testis at the highest dOSe (125 mg/kg).     

三硝基甲苯对雄性生殖毒性的研究

急性、亚急性和亚慢性TNT染毒大鼠睾丸铜锌含量和多种酶活性皆有所变化;睾丸和血清睾酮含量下降。大鼠辜丸游离间质细胞与TNT共同孵育时,睾酮形成量明显下降;间质细胞与TNT孵育后,活性氧与脂质过氧化阳性物质含量明显增加。补锌在一定程度上能拮抗TNT对大鼠的生殖毒性。横断面调查表明,TNT接触男工自觉性功能降低者增加,血清睾酮含量下降,精液常规检查有阳性所见。     

A Quantitative Method of Evaluating the Diuretic Response to Furosemide in Rats

Furosemide effects are usually evaluated by measuring the urinary excretion rate of Na⁺ (UV_Na) in humans. In the present study, however, UV_Na showed a nonlinear relationship with urine flow rate after intravenous injection of furosemide in rats. In contrast, when the urinary excretion rate of (Na⁺ + K⁺) (UV_Na+K) was plotted against the urine flow rate, a linear regression line was observed, with small interindividual variations in normal rats and in rats with uranyl nitrate-induced acute renal failure (ARF). Piretanide, a loop diuretic, also showed a similar relationship, while other types of diuretics revealed different slope values for the relationship. Although the urinary excretion rate of Cl^– (UV_C1) vs UV_Na+K is expected to show a linear relationship in normal rats, the correlation coefficient of the linear regression line was smaller than that of the urine flow rate vs UV_Na+K. Further, the slope of UV_C1 vs UV_Na+K was slightly different in ARF rats. Therefore, UV_Na+K provides a better quantitative measure of diuretic response to loop diuretics than UV_Na or UV_C1.     

A Novel Method for the Preclinical Assessment of Rectal Irritation

The purpose of this study concerns a novel method for preclinical assessment of rectal irritation caused by suppositories introduced into the rectum. Rectal irritation was assessed by the balloon method in fasting conscious rats. This method is based on measuring rectal contractions due to possible irritation caused by the presence of drugs and adjuvants in the suppository. In control experiments (vehicle only), significant rectal contractions were not observed in a range of pH 1.5–11.0 and osmotic pressure 70–2000 mOsm kg^?1 H₂O, respectively. On the other hand, strong contractions were observed after rectal administration of an aqueous solution of 50% glycerin, 100 mm sodium caprate or 25 mm sodium cholate. The intensity of contraction after rectal administration of sodium caprate or sodium cholate was dependent on the concentration in the dosing solution. In addition, the effect of sodium caprate and sodium cholate on rat rectal mucosa was investigated by optical light microscopy. Although slight or moderate alteration such as the presence of mucinous substance in lumen and congestion, oedema and haemorrhage of the rectal membrane 20 min after rectal administration, there was no major damage to the rectal mucosa. There was a correlation between the median score for mucinous substance in lumen and mean intensity of rectal contraction. For comparative purposes, defecating sensations, pain, itch, burning sensations, and awareness of the presence of a foreign body after administration of suppositories containing 0, 1, 2 and 4% sodium caprate were examined in eight healthy volunteers. The defecating sensation in the human subjects correlated with the intensity of rectal contraction in rats. The results suggest that rectal contraction in conscious rats could be a useful index for prediction of a defecating sensation in man.     

Population-level Assessment of Risks of Pesticides to Birds and Mammals in the UK

It is generally acknowledged that population-level assessments provide a better measure of response to toxicants than assessments of individual-level effects. Population-level assessments generally require the use of models to integrate potentially complex data about the effects of toxicants on life-history traits, and to provide a relevant measure of ecological impact. Building on excellent earlier reviews we here briefly outline the modelling options in population-level risk assessment. Modelling is used to calculate population endpoints from available data, which is often about individual life histories, the ways that individuals interact with each other, the environment and other species, and the ways individuals are affected by pesticides. As population endpoints, we recommend the use of population abundance, population growth rate, and the chance of population persistence. We recommend two types of model: simple life-history models distinguishing two life-history stages, juveniles and adults; and spatially-explicit individual-based landscape models. Life-history models are very quick to set up and run, and they provide a great deal of insight. At the other extreme, individual-based landscape models provide the greatest verisimilitude, albeit at the cost of greatly increased complexity. We conclude with a discussion of the implications of the severe problems of parameterising models.H.R. Akçakaya and C.J. Topping are principal authors of the RAMAS and ALMaSS software packages, respectively.     

环磷酰胺对雄性生殖系统毒性损伤的研究进展

环磷酰胺(cyclophosphamide,CP)是目前常用的一种烷化剂类抗肿瘤药物,临床常用于各种恶性肿瘤的化疗、类风湿关节炎及自身免疫性疾病的治疗。CP的常见不良反应包括肝肾功能损伤、出血性膀胱炎、恶心、呕吐、骨髓抑制等,然而目前备受关注的是CP对雄性生殖系统的毒性损伤。研究[1]发现,给大鼠一次性腹腔注射CP,剂量在75 mg/kg以上可造成明显生育能力损害。CP对雄性生殖系统的损伤和对后代的潜在致畸危险,已引起社     

A Novel Method to Radiolabel Gastric Retentive Formulations for Gamma Scintigraphy Assessment

Purpose. To develop a robust radiolabeling technique to enable evaluation of difficult to radiolabel gastric retentive formulations using gamma scintigraphy. The use of a successful radiolabel will allow accurate assessment of the gastric residence time of the formulations. Materials and Methods. The retention of two radionuclides, indium (¹¹¹In) and samarium (¹⁵³Sm), with and without further processing to improve radiolabel performance were evaluated in simulated gastric pH in vitro. The most successful formulation from the in vitro screening was further evaluated in preclinical and clinical studies. Results. In vitro evaluation revealed significant radionuclide leakage at pH 1.5 for most radiolabeling attempts. Radionuclide leakage at pH 4.5 was less pronounced. The most successful radiolabel was formulated by adsorbing indium chloride onto activated charcoal, followed by entrapment in a cellulose acetate polymer melt. This provided the best radiolabel retention under both pH conditions in vitro. The radiolabel also proved to be successful during preclinical and clinical evaluations, allowing evaluation of gastric retention performance as well as complete gastrointestinal transit. Conclusion. A simple, yet robust radiolabel was developed for gastric retentive formulations to be evaluated pre-clinically or in a clinical setting by entrapping the radionuclide in an insoluble polymer through a simple polymer melt process.