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Biodegradable Polymers as Drug Carrier Systems
Published in Severian Dumitriu, Valentin Popa, Polymeric Biomaterials, 2020
The biodegradation of polyesters was reviewed by Lewis (1990), Gopferich (1997), and Holland et al. (1986). The molecular weight and polydispersity as well as the crystallinity and morphology of the polymers are important factors in polymer biodegradation. Polyesters mainly undergo bulk erosion, i.e., the polymeric matrices degrade all over their cross-section and have erosion kinetics that are nonlinear and usually characterized by a discontinuity (Vert 2005). The factors that may affect the polylactide degradation include chemical and configurational structure, molecular weight and distribution, fabrication conditions, site of implantation, physical factors, and degradation conditions (Nakamura et al. 1989). The degradation of semi-crystalline polymers proceeds in two phases; in the first phase, the amorphous regions are hydrolyzed and then the crystalline regions. The polymers degraded by bulk hydrolysis of the ester bonds, which resulted in a decrease in molecular with no weight loss.
Cytotoxicity and maternal toxicity attributed to exposure to Momordica charantia L. (Cucurbitaceae) dry leaf extract
Published in Journal of Toxicology and Environmental Health, Part A, 2023
Ana Luisa Trautenmuller, Jonathan de Almeida Soares, Kamila Campos Behm, Laura Maria Marques Guimarães, Kássia Roberta Xavier-Silva, Anielly Monteiro de Melo, Graziele Alícia Batista Caixeta, Joelma Abadia Marciano de Paula, Elisa Flávia Luiz Cardoso Bailão, Vanessa Cristiane Santana Amaral
The experimental protocol of this study was conducted as previously described by Cardoso et al. (2017) and following the recommendations of the Brazilian National Health Surveillance Agency (Anvisa 2013). During pregnancy, females were evaluated for presence of clinical and behavioral signs of toxicity (piloerection, diarrhea, seizures, bleeding). Behavioral changes, mortality numbers, body weight, water, and feed intake were recorded daily. On GD 21, female rats were anesthetized with 25% urethane (0.5 ml/100 g body weight i.p.). Then, a laparotomy was performed to remove the ovaries and uterine horns, and collect the fetuses and their placentae. The gravid uterus was weighed and dissected to count live and dead fetuses, implantation sites, and resorption. The fetal and placental weights were recorded, and corpora lutea counted.
Effects of whole-body vibration on reproductive physiology in a rat model of whole-body vibration
Published in Journal of Toxicology and Environmental Health, Part A, 2022
K. Krajnak, S. Waugh, D. Welcome, X.S. Xu, C. Warren, W. McKinney, R.G. Dong
As mentioned above, maintenance of internal biological and physiological rhythms is also critical for normal reproductive functions in both males and females, and changes in feeding behavior in vibration-exposed animals may have altered expression of rhythms in reproductive tissue physiology. Food intake, along with the period of light and dark during the 24 hr cycle, serves as factors for entraining internal biological rhythms (Hosono et al. 2021). Internal rhythms are partially generated by a number of “clock” genes, one of which is the Period1 or Per1 gene (Rosenwasser and Turek 2015). The change in Per1 expression in the uterus and ovary may have been attributed to a shift in circadian expression of these genes rather than an overall decrease in expression (Fahrenkrug et al. 2006; He et al. 2007). A shift or general change in the expression of this gene in these tissues may disrupt cyclic development of follicles and generation of reproductive cycles (Fahrenkrug et al. 2006), and potentially cyclic alterations in the uterus that are necessary to support implantation and maintenance of pregnancy. Additional studies examining changes in expression of the transcription of Per1, other clock genes, and hormones and receptors involved in regulating reproduction, over a 24 hr period after treatment would determine if exposure to WBV disrupts the circadian clock in these tissues and if these observed alterations in part underlie reproductive dysfunction.
Optimisation and performance evaluation of an environmentally friendly rocket composite propellant
Published in Indian Chemical Engineer, 2019
Gbadebo Omoniyi Adeniyi, Jamiu Adetayo Adeniran, Adewole Johnson Adesanmi, Funsho Alaba Akeredolu, Jacob Ademola Sonibare
Many researches on composite solid propellants have been performed over the past few decades and much progress has been made [5–7]. However, most of the propellants were made with constituents (ammonium perchlorate, magnesium, boron) that are hazardous to lives and properties. Ammonium perchlorate-based propellant liberates hydrochloric acid which is environmentally undesirable [8]. Magnesium present in the propellant is attributed to the emissions of dangerous magnesium oxide [9]. Ammonium nitrate produces purely gaseous products. This reduces the amount of particulate emissions. However, this constituent has a low surface temperature and a low burn rate. The decomposition chemistry of ammonium nitrate is largely responsible for the low energy released [10]. Thus, this makes the ignition of the propellant a big challenge. Ammonium dinitramide decomposes very rapidly and is potentially a good propellant [11–13]. However, this constituent from the reproductive, fertility, pre-implantation and post-implantation studies is embryotoxic, and a mouse embryo toxicity study also showed that ADN affects the embryo [14]. Therefore, design or improving the propellant performances which meet future emissions regulations with a minimal pollution cost penalty, an optimised mixture ratio, good ballistic characteristics and readily available constituents is of great importance and remains highly empirical.