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Chemical Clearing of Brains
Published in Francesco S. Pavone, Shy Shoham, Handbook of Neurophotonics, 2020
Klaus Becker, Christian Hahn, Nina Jährling, Marko Pende, Inna Sabdyusheva-Litschauer, Saiedeh Saghafi, Martina Wanis, Hans-Ulrich Dodt
In 1989, Murray developed a clearing cocktail consisting of 1 vol. parts benzyl alcohol (BA) and 2 vol. parts benzyl benzoate (BB) that over years became a standard for clearing biological samples in the field of embryological and developmental research (Dent et al., 1989; Klymkowsky and Hanken, 1991). This mixture, which is commonly termed BABB or “Murray’s clear”, clears many kinds of samples excellently in a time range of a few hours or days. An entire juvenile mouse brain or mouse embryo is rendered virtually completely transparent within three days (Figure 9.3A–B). As with other lipophilic clearing agents, it is crucial that the samples are completely dehydrated before clearing. Minute residuals of water can be removed by brief incubation in an apolar solvent as hexane following the last dehydration step (Dodt et al., 2007). As with other organic solvents BABB severely quenches the fluorescence of genetic markers as GFP, if the incubation times are longer than a few hours or it contains peroxides. Nevertheless, BABB can be successfully applied to GFP expressing mouse brains and embryos, if the GFP expression rate is sufficiently high and incubation times are not too long (Figure 9.3C–D) (Dodt et al., 2007). However, newer clearing approaches with better GFP compatibility as 3DISCO generally provides a superior alternative for samples expressing genetic markers (Becker et al., 2012; Ertürk et al., 2012).
Use of Physiological and Biochemical Measures in Pollution Biology
Published in Alan G. Heath, Water Pollution and Fish Physiology, 2018
Because of the time and expense involved, there has been considerable effort expended to develop modified forms of fish and invertebrate life cycle tests that will yield essentially the same information as one which is complete. In essence, that has meant identifying the most sensitive stages and concentrating on those. McKim (1977) evaluated 56 studies in which complete or partial life cycle tests were carried out and concluded that the embryo-larval and early juvenile life stages were the most sensitive in most cases. The biological measures of sensitivity were decreases in hatchability, survival and growth, and deformities in the juveniles. More recently, Landner et al. (1985) have shown that exposure of the adults before spawning to a mixed effluent can cause severe effects on the subsequent embryos and larvae, which again emphasizes the sensitivity of the young.
Fish
Published in E. B. Welch, J. M. Jacoby, T. Lindell, Pollutant Effects in Freshwater, 2004
E. B. Welch, J. M. Jacoby, T. Lindell
Feminization and other reproductive and developmental abnormalities in wild fish due to exposure to oestrogen mimickers in sewage effluent have been reported in a number of studies (e.g. Purdom et al., 1994; Jobling et al., 1998; Rodgers-Gray et al., 2000). These effects are not limited to fish. Developmental abnormalities in embryos and hatchlings of snapping turtles from the Great Lakes Region were found to be related to dibenzodioxins and dibenzofurans (Bishop et al., 1998). Developmental and reproductive abnormalities in hatchling and juvenile alligators (Alligator mississippiensis) in Lake Apopka, Florida, were linked to exposure to endocrine-disrupting chemicals during embryo development (Guillette et al., 1999). Endocrine disruption in birds and mammals has also been reported (Colborn et al., 1993 ; Tyler et al., 1998).
Effects of 17α-ethinylestradiol on the neuroendocrine gonadotropic system and behavior of European sea bass larvae (Dicentrarchus labrax)
Published in Journal of Toxicology and Environmental Health, Part A, 2023
S Soloperto, S Olivier, A Poret, C Minier, MP Halm-Lemeille, C Jozet-Alves, S Aroua
Disruption of kiss expression might lead to differing effects depending upon the type and timing of exposure. In juvenile and adult sea bass, some investigators noted the involvement of kiss2/gnrh1 systems in the control of gonadotropic activity (Espigares et al. 2015), and of kiss1/gnrh2 in association between integration of environmental stimuli (i.e. photoperiod) and the onset of puberty (Espigares et al. 2017). Studies carried out during early developmental stages led to somewhat different results. While normal development was observed in kiss1 and kiss2 knockout zebrafish (Tang et al. 2015), kiss1 knockdown induced a major disruption of embryonic and brain development in medaka (Hodne et al. 2013). Therefore, XEs exposure might lead to varying adverse effects depending upon the species and exposure window. In the case of the European sea bass, further research is needed to identify the developmental roles and potential adverse effects exerted by a disruption of kiss expression.
A new early Miocene archaic dolphin (Odontoceti, Cetacea) from New Zealand, and brain evolution of the Odontoceti
Published in New Zealand Journal of Geology and Geophysics, 2023
Yoshihiro Tanaka, Megan Ortega, R. Ewan Fordyce
Ontogenetic variation needs to be considered carefully to avoid mixing shapes formed by growth and evolution. We consider that having a deep sylvian fissure is related to encephalization, as the fissure gets deeper while the cerebrum expands throughout ontogeny. This observation is based on Phocoena phocoena endocasts (Racicot & Colbert 2013). Our comparison supports Bisconti et al. (2021), who reported that the length of the sylvian fissures may be related to the length of the temporal lobe, which is a part of the increase in encephalization. The median sulcus is interpreted to have no major ontogenetic variation after birth, which is supported by a modern sequence of Phocoena phocoena endocasts, ranging from juvenile to adult (Racicot & Colbert 2013), and a study of embryo to juvenile brains in Stenella coeruleoalban (Kamiya & Pirlot 1980). Thus, the median sulcus appears to show more evolutionary trends of the cerebrum (Figure 2).