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Reproductive and Developmental Toxicity
Published in Frank A. Barile, Barile’s Clinical Toxicology, 2019
Anirudh J. Chintalapati, A. Barile Frank
Fetal development involves the gradual establishment and modification of anatomical structures from its beginning at fertilization (conception) to maturity. Figure 32.1 illustrates the phases of embryonic and fetal development as they occur within the trimesters. This figure denotes how the first 12 weeks roughly correspond to the first trimester. This phase is characterized as the period of time for embryonic development, when the fertilized ovum differentiates into precursor stem cells, which progress to the launching of fetal membranes and the embryonic disc (weeks 1–3, embryo). The remainder of the pregnancy (13 to 38 weeks) is dedicated to fetal development, when the established blueprints of organs and tissues undergo further growth and maturity. Together, the two processes occurring during the weeks of embryonic and fetal expansion are referred to as prenatal development. Thus, in humans, the gestational period is normally of 9 months’ duration (38 weeks or 280 days from the first day of the last menstrual period, assuming a regular 28 day cycle). Postnatal development therefore begins at birth and progresses to maturity (i.e., for approximately 18 years). Particular events that distinguish the trimesters in Figure 32.1 are further described in the following subsection.
Animal diseases
Published in Jim Cox, Iain Mungall, Rural Healthcare, 2017
The bovine gestation period is 9 months. In both dairy and beef herds the farmer’s aim is to attain a calving index of 365 days, i.e. a calf born by each cow every 12 months. To achieve this, a cow should conceive 90 days after calving. This is the optimum interval for maximum milk output and calf production without detriment to the cow. Like sheep and horses, cows ovulate approximately every 21 days and display oestrus behaviour at this time. Rectal palpation or ultrasound per rectum 24–28 days post conception can confirm pregnancy. Poor ovulation and absent oestrus behaviour occur commonly when a cow is ‘milking off its back’, i.e. its food intake is inadequate.
Animal Models of Human Respiratory Viral Infections
Published in Sunit K. Singh, Human Respiratory Viral Infections, 2014
Kayla A. Weiss, Cory J. Knudson, Allison F. Christiaansen, Steven M. Varga
In addition to the anatomical and physiological advantages of their pulmonary system, a number of additional factors contribute to the advantages associated with using ferrets to study human respiratory viral infections. Their litter size is approximately six to eight with a short gestation period of 7 weeks. Ferrets are also relatively inexpensive to house and feed though the cost is still greater than other small rodents.70 The smaller size of ferrets makes them easier to handle than larger animals. In addition, ferrets are a well-established model for IAV infection and for the study of respiratory virus transmission. The lack of commercially available antibodies and reagents is a limitation of ferrets as an animal model. There are also few vendors that sell ferrets and there are very few genetically modified strains of ferrets available. These limitations make it difficult to assess the role of specific genes. Furthermore, due to the lack of sequencing for the entire ferret genome, their degree of genetic similarity to humans is currently unclear.
Does the timing of antibiotic exposure in pregnancy impact the risk of development of pediatric asthma?: A systematic review and meta-analysis
Published in Journal of Asthma, 2023
Liping Wang, Xiaomei Hu, Caixia Xiang
The gestational period constitutes one of the most crucial times of growth and development. At this stage, the fetus is highly susceptible to any kind of exogenous exposure that could disbalance the delicate biological process leading to adverse outcomes (7). According to a hypothesis put forward by Baker et al. (8), chronic long-term illnesses could have their origins in intrauterine and early postnatal life and it is, therefore, important to monitor and prevent unnecessary environmental exposures to reduce future disease burden. In this context, several researchers have explored associations between different maternal illnesses and environmental exposures and subsequent risk of asthma in the offspring. Studies suggest that gestational diabetes, hypertensive disorders of pregnancy, maternal nutrition, adverse chemical exposure, maternal intake of drugs, and maternal lifestyle; all have a role in the development of childhood asthma (9–12).
A systematic review on fluoride-induced epigenetic toxicity in mammals
Published in Critical Reviews in Toxicology, 2022
Satheeswaran Balasubramanian, Ekambaram Perumal
The interpretation of the reported findings is hindered by the factors such as the type of tissue used, dosage, duration, species, cell type, the method used for analyses, sample size, and more. One of the major factors is the species-specific difference in the epigenetic pattern during development. Further, it is difficult to correlate the results between two different tissues, as each tissue has its specific epigenetic pattern. The biphasic effect (i.e. mitogenic at low concentrations whereas toxic at higher dosages) of fluoride has not been elucidated in detail. For example, a person exposed to 1–10 ppm of fluoride will have a plasma fluoride level of 1–10 μM, whereas to obtain a similar effect in rats, 25–100 ppm should be used (DenBesten and Li 2011). Most of the studies (except epidemiological studies) failed to measure fluoride content in tissues. This is further complicated by the difference in the gestational period between rodents (rats and mice) and humans. Likewise, people suffering from skeletal fluorosis are exposed to fluoride transgenerationally, but this has not been reproduced in experimental models for epigenetic effects.
Gestational exposure to silver nanoparticles enhances immune adaptation and protection against streptozotocin-induced diabetic nephropathy in mice offspring
Published in Nanotoxicology, 2022
Ratnakar Tiwari, Radha Dutt Singh, Sukhveer Singh, Diksha Singh, Anurag Kumar Srivastav, Mahadeo Kumar, Vikas Srivastava
The gestational period is considered a highly susceptible time window and stress encountered during this period may lead to health complications later in life. Adverse intrauterine environments such as exposure to noxious toxins, pollutants, stress, and inflammation have been associated with the development of chronic diseases in offspring, including diabetes (de Rooij et al. 2006; Li et al. 2017; McGlinchey et al. 2020), obesity (Fan et al. 2020; Lauritzen et al. 2018), chronic kidney diseases (CKD) (Srivastava et al. 2021; Tiwari et al. 2021; Wang et al. 2018), hypertension (Dodic et al. 2002; Farzan et al. 2018), and cancer (Waalkes et al. 2008). To cope with intrauterine stress, developing fetuses change their physiology, including the structures and functions of different tissues (Brenner and Chertow 1994; Clark 1998; Lithell et al. 1996). Adaptations to intrauterine stress likely protect fetal development, but irreversible changes may adversely affect offspring’s health later in life, as proposed in the Developmental Origin of Health and Disease hypothesis (DOHaD) (Barker and Osmond 1986). Interestingly, contradictory to DOHaD, emerging evidence indicates that adverse gestational conditioning can also enhance the protective response of offspring against adverse conditions later in life (Lim et al. 2021) which suggests the complex and context-dependent effect of gestational conditioning on offspring’s health.