The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Louis J Guillette - One of the best experts on this subject based on the ideXlab platform.
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trace element biodistribution in the american Alligator Alligator mississippiensis
Chemosphere, 2017Co-Authors: Arnold M Brunell, Frances M Nilsen, Brittany L Kassim, Ted Lange, Patrick J Delaney, Stephen E Long, Louis J Guillette, Tracey B SchockAbstract:Routine monitoring of contaminant levels in wildlife is important for understanding chemical exposure and ultimately the link to ecosystem and human health. This is particularly important when the monitored species is recreationally hunted for human consumption. In the southeastern United States, recreational Alligator harvesting takes place annually and in locations that are known to be contaminated with environmental pollutants. In this study, we investigated the biodistribution of trace elements in the American Alligator (Alligator mississippiensis) from five sites in Florida, USA. These sites are locations where annual recreational Alligator harvesting is permitted and two of the sites are identified as having high mercury contamination with human consumption advisories in effect. We utilized routinely collected monitoring samples (blood and scute), a commonly consumed tissue (muscle), and a classically analyzed tissue for environmental contaminants (liver) to demonstrate how the trace elements were distributed within the American Alligator. We describe elemental tissue compartmentalization in an apex predator and investigate if noninvasive samples (blood and scute) can be used to estimate muscle tissue concentrations for a subset of elements measured. We found significant correlations for Hg, Rb, Se, Zn and Pb between noninvasive samples and consumed tissue and also found that Hg was the only trace metal of concern for this population of Alligators. This study fills a gap in trace elemental analysis for reptilian apex predators in contaminated environments. Additionally, comprehensive elemental analysis of routinely collected samples can inform biomonitoring efforts and consumption advisories.
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identification and characterization of the androgen receptor from the american Alligator Alligator mississippiensis
Endocrinology, 2015Co-Authors: Shinichi Miyagawa, Brenna M Doheny, Ryohei Yatsu, Yukiko Ogino, Yoshinao Katsu, Satomi Kohno, Louis J Guillette, Hiroshi Ishibashi, Yasuhiko Ohta, Taisen IguchiAbstract:Androgens are essential for the development, reproduction, and health throughout the life span of vertebrates, particularly during the initiation and maintenance of male sexual characteristics. Androgen signaling is mediated by the androgen receptor (AR), a member of the steroid nuclear receptor superfamily. Mounting evidence suggests that environmental factors, such as exogenous hormones or contaminants that mimic hormones, can disrupt endocrine signaling and function. The American Alligator (Alligator mississippiensis), a unique model for ecological research in that it exhibits environment-dependent sex determination, is oviparous and long lived. Alligators from a contaminated environment exhibit low reproductive success and morphological disorders of the testis and phallus in neonates and juveniles, both associated with androgen signaling; thus, the alterations are hypothesized to be related to disrupted androgen signaling. However, this line of research has been limited because of a lack of informatio...
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endogenous and exogenous estrogens during embryonic development affect timing of hatch and growth in the american Alligator Alligator mississippiensis
Comparative Biochemistry and Physiology B, 2015Co-Authors: Lori Cruze, Alison Mccombe Roark, Gabrielle Rolland, Mona Younas, Nicole I Stacy, Louis J GuilletteAbstract:Abstract Prenatal exposure to estrogenic endocrine disrupting chemicals (EDCs) can affect length of gestation and body mass and size of offspring. However, the dose, timing, and duration of exposure as well as sex and strain of the experimental animals determine the direction and magnitude of these effects. In this study, we examined the effects of a one-time embryonic exposure to either 17 β-estradiol (E2) or bisphenol A (BPA) on rate of development and growth in American Alligators ( Alligator mississippiensis ). Our results indicate that BPA and E2-treated Alligators hatched approximately 1.4 days earlier than vehicle-treated (control) Alligators, suggesting that estrogenic chemicals hasten hatching in these animals. We assessed growth rates, growth allometry, and body condition for 21 weeks after hatching and found that BPA-treated Alligators grew more quickly shortly after hatching but more slowly thereafter compared to control Alligators. Conversely, E2-treated Alligators grew more slowly shortly after hatching but more quickly thereafter compared to control Alligators. As a result of differences in growth rate, BPA-treated Alligators were heavier, longer, and fatter than control Alligators at age 5 weeks but were similar in size and leaner than control Alligators at age 21 weeks. Biochemical analytes were examined at the end of the 21-week study to assess overall metabolic condition. We found that E2-treated Alligators had significantly higher circulating plasma concentrations of cholesterol and triglycerides than control Alligators while BPA-treated Alligators had blood profiles comparable to control Alligators. Our results provide important insights into the effects of exogenous estrogens on morphology and metabolism in an oviparous, semi-aquatic reptile.
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animal borne imaging reveals novel insights into the foraging behaviors and diel activity of a large bodied apex predator the american Alligator Alligator mississippiensis
PLOS ONE, 2014Co-Authors: James C Nifong, Louis J Guillette, Brian R Silliman, Russell H Lowers, Rachel L Nifong, Jake M Ferguson, Matthew Welsh, Kyler Abernathy, Greg MarshallAbstract:Large-bodied, top- and apex predators (e.g., crocodilians, sharks, wolves, killer whales) can exert strong top-down effects within ecological communities through their interactions with prey. Due to inherent difficulties while studying the behavior of these often dangerous predatory species, relatively little is known regarding their feeding behaviors and activity patterns, information that is essential to understanding their role in regulating food web dynamics and ecological processes. Here we use animal-borne imaging systems (Crittercam) to study the foraging behavior and activity patterns of a cryptic, large-bodied predator, the American Alligator (Alligator mississippiensis) in two estuaries of coastal Florida, USA. Using retrieved video data we examine the variation in foraging behaviors and activity patterns due to abiotic factors. We found the frequency of prey-attacks (mean = 0.49 prey attacks/hour) as well as the probability of prey-capture success (mean = 0.52 per attack) were significantly affected by time of day. Alligators attempted to capture prey most frequently during the night. Probability of prey-capture success per attack was highest during morning hours and sequentially lower during day, night, and sunset, respectively. Position in the water column also significantly affected prey-capture success, as individuals’ experienced two-fold greater success when attacking prey while submerged. These estimates are the first for wild adult American Alligators and one of the few examples for any crocodilian species worldwide. More broadly, these results reveal that our understandings of crocodilian foraging behaviors are biased due to previous studies containing limited observations of cryptic and nocturnal foraging interactions. Our results can be used to inform greater understanding regarding the top-down effects of American Alligators in estuarine food webs. Additionally, our results highlight the importance and power of using animal-borne imaging when studying the behavior of elusive large-bodied, apex predators, as it provides critical insights into their trophic and behavioral interactions.
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altered gonadal expression of tgf β superfamily signaling factors in environmental contaminant exposed juvenile Alligators
The Journal of Steroid Biochemistry and Molecular Biology, 2011Co-Authors: Brandon C Moore, Yoshinao Katsu, Satomi Kohno, Louis J Guillette, Taisen Iguchi, Matthew R Milnes, Teresa K WoodruffAbstract:Abstract Environmental contaminant exposure can influence gonadal steroid signaling milieus; however, little research has investigated the vulnerability of non-steroidal signaling pathways in the gonads. Here we use American Alligators (Alligator mississippiensis) hatched from field-collected eggs to analyze gonadal mRNA transcript levels of the activin–inhibin–follistatin gene expression network and growth differentiation factor 9. The eggs were collected from Lake Woodruff National Wildlife Refuge, a site with minimal anthropogenic influence, and Lake Apopka, a highly contaminated lake adjacent to a former EPA Superfund site. The hatchling Alligators were raised for 13 months under controlled conditions, thus limiting differences to embryonic origins. Our data reveal sexually dimorphic mRNA expression in 13-month-old Alligator gonads similar to patterns established in vertebrates with genetic sex determination. In addition, we observed a relationship between lake of origin and mRNA expression of activin/inhibin subunits α and βB, follistatin, and growth differentiation factor 9. Our study suggests that embryonic exposure to environmental contaminants can affect future non-steroidal signaling patterns in the gonads of a long-lived species.
Xiaobing Wu - One of the best experts on this subject based on the ideXlab platform.
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molecular cloning of androgen receptor and gene expression of sex steroid hormone receptors in the brain of newborn chinese Alligator Alligator sinensis
Gene, 2018Co-Authors: Yongkang Zhou, Ali Izaz, Mengjuan Wu, Ruidong Zhang, Renping Wang, Ying Zhang, Xiaobing WuAbstract:Abstract Sex steroid hormones play an important role in mediating physiological responses and developmental processes through their receptors across all vertebrates. Chinese Alligator (Alligator sinensis) is a critically endangered reptile species unique to China. In this study, we have cloned one of the sex steroid hormone receptor genes, androgen receptor (AR) from the brain of Chinese Alligator for the first time. The full-length AR cDNA is 2717 bp in length with an open reading frame (ORF) encoding 722 amino acids. Amino acid alignment analyses indicated that the ARs exhibit highly conserved functional domains. Especially, the P-box and D-box, which are essential to ensure that receptor binding to the androgen response elements, are completely conserved in selected species. Using the quantitative real-time PCR (qPCR), the spatial expression of four receptor mRNAs in all newborn brain tissues and temporal expression of them in the cerebrum during the embryonic development in Chinese Alligators were investigated. The results of qPCR showed ubiquitous expression of the four receptor mRNAs in all newborn brain tissues examined and significant changes in the expression levels of these receptor mRNAs in the embryonic development. These results suggest that sex steroid hormones might play an important role in the regulation of complex neuroendocrine activities in newborn Chinese Alligator. Furthermore, these data provide an important foundation for further studies on endocrinology and molecular biology of non-mammalian sex steroid hormone receptors.
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insights into the seasonal adaptive mechanisms of chinese Alligators Alligator sinensis from transcriptomic analyses
Australian Journal of Zoology, 2018Co-Authors: Fang Zhang, Yongkang Zhou, En Li, Rong Wu, Xiaobing WuAbstract:The Chinese Alligator (Alligator sinensis) is an endemic and rare species in China, and is considered to be one of the most endangered vertebrates in the world. It is known to hibernate, an energy-saving strategy against cold temperatures and food deprivation. Changes in gene expression during hibernation remain largely unknown. To understand these complex seasonal adaptive mechanisms, we performed a comprehensive survey of differential gene expression in heart, skeletal muscle, and kidney of hibernating and active Chinese Alligators using RNA-Sequencing. In total, we identified 4780 genes differentially expressed between the active and hibernating periods. GO and KEGG pathway analysis indicated the likely role of these differentially expressed genes (DEGs). The upregulated DEGs in the active Chinese Alligator, CSRP3, MYG and PCKGC, may maintain heart and skeletal muscle contraction, transport and storage of oxygen, and enhance the body’s metabolism, respectively. The upregulated DEGs in the dormant Chinese Alligator, ADIPO, CIRBP and TMM27, may improve insulin sensitivity and glucose/lipid metabolism, protect cells against harmful effects of cold temperature and hypoxia, regulate amino acid transport and uptake, and stimulate the proliferation of islet cells and the secretion of insulin. These results provide a foundation for understanding the molecular mechanisms of the seasonal adaptation required for hibernation in Chinese Alligators, as well as effective information for other non-model organisms research.
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molecular characterization and tissue expression profiles of insulin like growth factor binding protein 1 igfbp 1 in chinese Alligator Alligator sinensis during the active and hibernating periods
Biologia, 2018Co-Authors: Mengyun Li, Yongkang Zhou, Shengzhou Zhang, Ting Meng, Fei Peng, Xiaobing WuAbstract:The Chinese Alligator Alligator sinensis (Fauvel, 1879) is an endangered species endemic to China. Up to this date, very little is known about the regulation of its growth and development. Insulin-like growth factor binding protein-1 (IGFBP-1) plays essential roles in regulating vertebrate growth and development by modulating IGFs action. In this study, we cloned the full-length cDNA of Chinese Alligator IGFBP-1 (caIGFBP-1) for the first time, which has an open reading frame (ORF) of 885-bp nucleotides encoding a peptide of 294 amino acid residues. The caIGFBP-1 contains all features of IGFBP-1 peptide with the conserved cysteine-rich N- and C-terminal domains and variable central L-domain. Multiple alignment analysis showed that caIGFBP-1 shares high identity in amino acid sequence with the IGFBP-1 s of American Alligator Alligator mississippiensis (Daudin, 1802) (99.32%) and birds (66.32–74.53%). Phylogenetic tree analysis of IGFBP-1 amino acid sequences indicated that Alligators cluster into bird branch. The caIGFBP-1 is widely expressed in all the examined tissues, the expression level is highest in liver, higher in kidney, moderate in pancreas, stomach, small intestine, and lower in ovary, muscle, lung, heart. During the hibernating period, the expression level of caIGFBP-1 was significantly reduced in liver, kidney, stomach, pancreas and small intestine, while did not significantly change in heart, lung, ovary and muscle. The caIGFBP-1 mRNA expression changes during the active and hibernating periods, which coincides with that of Chinese Alligator IGF, implicating that it might play important roles in the IGF-mediated growth and development of Chinese Alligator.
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molecular cloning of esr2 and gene expression analysis of esr1 and esr2 in the pituitary gland of the chinese Alligator Alligator sinensis during female reproductive cycle
Gene, 2017Co-Authors: Ruidong Zhang, Yongkang Zhou, Rong Wu, Xiaobing WuAbstract:Abstract Estrogens play critical roles in reproductive physiology via estrogen receptors (ESRs) in vertebrates, including reptiles. Chinese Alligator (Alligator sinensis) is an endemic and endangered reptile species in China. In the present study, we cloned ESR2 gene from the ovary using rapid amplification of cDNA ends (RACE), investigated the spatial expression of ESRs in various tissues and temporal expression of ESRs in the pituitary glands during the reproductive cycle in Chinese Alligators by quantitative real-time PCR (qPCR). Bioinformatics and phylogenetic analysis of deduced ESR2 protein were also performed. The full-length cDNA of the ESR2 is 1647 bp in length, with an open-reading frame encoding 548 amino acids. The bioinformatics analysis indicated that the deduced amino acid sequence of Alligator ESR2 was highly conserved with that of other vertebrate species. In addition, compared to human ESR2, the 14 amino acids in the Alligator ESR2 that are essential for specific recognition of estradiol are entirely conserved. The phylogenetic analysis showed that Alligators were more closely related to birds than to other reptiles. The results of qPCR showed that the tissue distribution patterns of both ESR subtype mRNAs appeared to be different. In male tissues, the highest mRNA level of both ESRs is in the liver. While in female tissues, ESR1 and ESR2 showed the highest mRNA level in the hypothalamus and pituitary gland, respectively. During the female reproductive cycle, the expression level of ESR1 mRNA increased from the initial post-hibernation period to the reproductive period, reached its peak in the reproductive period, and then decreased in the autumn active period and hibernation period. Conversely, the highest transcription level of ESR2 was observed in the hibernation period.
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insulin like growth factor i igf i in chinese Alligator Alligator sinensis molecular characterization tissue distribution and mrna expression changes during the active and hibernating periods
General and Comparative Endocrinology, 2017Co-Authors: Shengzhou Zhang, Yongkang Zhou, Rui Zhang, Shuai Zhao, Xiaobing WuAbstract:Abstract The Chinese Alligator Alligator sinensis is an endangered species endemic to China, up to date, little is known about the regulation of its growth and development. Insulin-like growth factor I (IGF-I) plays a vital role in regulating vertebrate growth and development. In this study, the full-length cDNA of IGF-I in Chinese Alligator (caIGF-I) was obtained for the first time, it contains 890-bp nucleotides encoding a 153-amino acid precursor, the mature caIGF-I consists of 70 amino acids by cleaving the signal peptide and C-terminal extension (E domain). The caIGF-I contains all the features of IGF-I peptide with B, C, A, and D domains and the six conservative cysteine residues involved in the stable tertiary structure. Multiple alignment analysis showed that the amino acid sequence of caIGF-I shares high identity with American Alligator Alligator mississippiensis (100%) and birds (95–97%). Phylogenetic tree analysis of the IGF-I amino acid sequences indicated that Alligators cluster into the bird branch. Real-time quantitative PCR technique showed that caIGF-I is widely expressed in all the examined tissues with the highest expression level in liver, higher in pancreas and oviduct while lower in heart, spleen, lung, kidney, stomach, intestines, ovary and muscles. During hibernation, the caIGF-I expression level decreased significantly in liver, pancreas, oviduct and kidney, while did not significantly change in heart, spleen, lung, stomach, small intestine, ovary and muscles. The mRNA expression changes during the two periods implicate that caIGF-I might play an important role in the regulation of feeding and growth in the Chinese Alligator.
Shengguo Fang - One of the best experts on this subject based on the ideXlab platform.
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multi omics analysis reveals that natural hibernation is crucial for oocyte maturation in the female chinese Alligator
BMC Genomics, 2020Co-Authors: Jianqing Lin, Hua Jiang, Yi Zhang, Qiuhong Wan, Shengguo FangAbstract:Hibernation in an appropriate environment not only is important for the survival of hibernators in winter, but also is crucial for breeding in the following season for many hibernating species. However, the genetic and epigenetic mechanism underlying this process remain unclear. In the current study, we performed an integrative multi-omics analysis of gonads collected from Chinese Alligators that overwintered in wild cave and artificial warmroom to explore transcriptomic and epigenomic alternations in these organs. The data revealed that in the breeding season, female Alligators were more strongly affected in terms of gene expression than males by non-hibernation because of overwintering in a warm room, especially for genes related to oocyte maturation, and this effect commenced in winter with the downregulation of STAR, which is the rate limiting factor of steroid biosynthesis. Further, miRNAs were found to play essential roles in this negative effect of overwintering in the warm room on hibernation. The upregulated miRNAs likely were responsible for the suppression of oocyte maturation in the breeding season. Finally, DNA methylome changes, especially hypomethylation, were found to play an important role in the alterations in ovarian function-related gene expression induced by non-hibernation. Our study revealed the crucial role of hibernation quality for oocyte maturation in the Chinese Alligator and the underlying genetic and epigenetic mechanisms, and highlights the importance of habitat, and especially, the overwintering site, in the conservation of not only the Chinese Alligator, but also other endangered hibernators.
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metagenomics reveals seasonal functional adaptation of the gut microbiome to host feeding and fasting in the chinese Alligator
Frontiers in Microbiology, 2019Co-Authors: Keyi Tang, Zhenwei Wang, Shengguo FangAbstract:Hibernator gut microbiomes vary seasonally with host physiology and food availability, but their functional potential and host–microbial interactions have not been well characterized. As a natural hibernator, the Chinese Alligator (Alligator sinensis) is an ideal and intriguing model to investigate changes in microbial community structure and function caused by hibernation. In this study, we used 16S rRNA profiling and metagenomic analysis to compare the microbiome composition, diversity, and functional capacity in the gut of hibernating versus active Chinese Alligators. Our results show that gut microbial communities undergo seasonal restructuring in response to seasonal cycles of feeding and fasting in the Chinese Alligator, but this animal harbors a core gut microbial community primarily dominated by Proteobacteria, Fusobacteria, Bacteroidetes and Firmicutes across the gut regions. During hibernation, there is an increase in the abundance of bacterial taxa (e.g., Bacteroidetes) that can degrade and utilize host mucin glycans, which allows adaptation to winter fasting. This is accompanied by the enrichment of mucin oligosaccharide-degrading enzyme and carbohydrate-active enzyme families. In contrast, during the active phase (feeding), active Chinese Alligators exhibit a carnivore gut microbiome dominated by Fusobacteria, and there is an increase in the relative abundance of bacteria (e.g., Cetobacterium somerae) with known proteolytic and amino acids-fermentating functions that improve host protein-rich food digestion efficiency. In addition, seasonal variations in the expression of β-defensins play a protective role in intestinal immunity. These findings provide insights into the functional adaptations of host–gut microbe symbioses to seasonal dietary shifts to maintain gut homeostasis and health, especially in extreme physiological states.
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the sex ratio of wild chinese Alligators Alligator sinensis
Current Zoology, 2013Co-Authors: Lan Zhao, Haiqiong Yang, Liming Fang, Shengguo FangAbstract:The Chinese Alligator Alligator sinensis is one of the most endangered crocodilian species, and typically exhibits temperature-dependent sex determination. It is extremely important to clarify the sex structure of Chinese Alligators to implement recovery projects successfully. However, the sex ratio of wild Chinese Alligators remains unknown. In this study, we collected 28 years of sex ratio data from Chinese Alligators residing in the natural and artificial habitats of Changxing Nature Reserve, China, and examined the differences in the sex ratio dynamics between these two populations. We observed that the sex ratio of wild Chinese Alligators is 1 male to 4.507 females, which was significantly lower compared to that of the captive population (1 to 2.040; P 0.05). Overall, this study indicates that the stabilized fe- male-biased sex ratio of Changxing Chinese Alligators might result from selection pressure caused by local mate competition and major inbreeding (Current Zoology 59 (6): 725-731, 2013).
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eleven novel microsatellite markers for the chinese Alligator Alligator sinensis
Conservation Genetics, 2009Co-Authors: Wei Jing, Xiaoliang Wang, Shengguo FangAbstract:Chinese Alligator (Alligator sinensis) is a critically endangered species endemic to China. In this study, we developed 11 novel microsatellite loci for this rare species and applied them to examine genetic variation of indigenous Alligators from Changxing Nature Reserve and America-born Chinese Alligators. The 11 polymorphic microsatellites presented a total of 31 alleles among 57 individuals scored, yielding an average of 2.82 alleles per locus. One allele was unique to the American population but four private alleles were detected in the Changxing population. The average expected and observed heterozygosities were 0.400 and 0.482 for the Changxing Alligators and 0.520 and 0.621 for the America-born individuals, respectively. These microsatellite markers would be useful tools in the genetic examination of this endangered species.
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heavy metal distribution in tissues and eggs of chinese Alligator Alligator sinensis
Archives of Environmental Contamination and Toxicology, 2006Co-Authors: Shengguo Fang, Qianghua Xu, Zhenwei Wang, Zhiping WangAbstract:Chinese Alligator (Alligator sinensis) is a critically endangered species endemic to China. Concentrations of heavy metals (As, Fe, Mn, Cu, Pb, Cd, Cr, Zn, and Hg) were examined in the tissues of Chinese Alligators to elucidate the background distribution of these metals in the Alligator body. Generally, within the body compartments, metal concentrations were high in liver, kidney, and heart, and low in pancreas and gonad. Study of heavy metal levels in the feces and eggs of Chinese Alligator suggested that Chinese Alligators could reduce body burden of toxic substances by excreting them to feces and/or sequestrating them into eggs to a lesser extent. In addition, to test whether eggshell or egg membrane could be used as surrogates to measure heavy metal load in egg contents, the correlation of metal concentrations between three egg compartments was determined. Of the nine elements analyzed, concentrations of iron, copper, and zinc in the shell membrane were highly correlated with the levels in egg contents, whereas no metal was significantly correlated between eggshell and egg contents. This suggested that the shell membrane could be a useful bioindicator for Fe, Cu, and Zn contaminations in the eggs of Chinese Alligator. In a comparison of metal contents in the eggs of individuals from the Anhui captive population, the wild population in Anhui Province, and those of the Changxing captive population, higher Cu, Zn, and Cd levels and a lower Pb level were found in the Changxing individuals, indicative of specific pollutants in different areas. In addition, the majority of metal elements in the muscles of Chinese Alligators and American Alligators are in the same ranges. As a result of the data found in the eggs of the two Alligator species, the Chinese Alligators may be exposed to a higher level of metal pollutants. The study provided measurement of the heavy metal distribution in the endangered Chinese Alligator for the first time and could serve as the background for the monitoring of possible heavy metal contaminations in the Alligator habitats.
Satomi Kohno - One of the best experts on this subject based on the ideXlab platform.
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oil dispersant corexit 9500 is weakly estrogenic but does not skew the sex ratio in Alligator mississippiensis
Journal of Applied Toxicology, 2020Co-Authors: Arnold M Brunell, Yoshinao Katsu, Satomi Kohno, Russell H Lowers, Nicole A Mcnabb, Melissa C Bernhard, Demetri D SpyropoulosAbstract:During the Deepwater Horizon oil spill, vast quantities of a chemical dispersant Corexit 9500 were applied in remediation efforts. In addition to the acute toxicity, it is essential to evaluate Corexit further with a broader scope of long-term sublethal endocrine endpoints. The American Alligator (Alligator mississippiensis) is an excellent organism for such an endeavor. It exhibits temperature-dependent sex determination, in which egg incubation temperatures during a thermosensitive period (TSP) in embryonic development determine the sex of embryos. Estrogen signals play a critical role in this process. For example, a single exposure to exogenous estrogen during the TSP overrides the effects of temperature and leads to skewed sex ratios. At a concentration of 100 ppm, Corexit significantly induced transcriptional activity of both Alligator nuclear estrogen receptors 1 and 2 in vitro in reporter gene assays. To investigate the estrogenic effects of Corexit on gonadal development, Alligator eggs were exposed to Corexit at environmentally relevant concentrations (0.25, 2.5 and 25 ppm) before the TSP in ovo. Exposure to Corexit at 0.25 and 25 ppm significantly delayed hatching and growth. Corexit exposure at any treatment level did not affect sex ratios or testicular mRNA abundance as measured at 1-week post-hatching, suggesting that the combination of Corexit components did not synergize enough to induce ovarian development in ovo. These results point to a need for further investigations on individual and combined components of Corexit to understand better their long-term effects on the development and reproductive health of Alligators and other coastal aquatic wildlife.
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improved genome assembly of american Alligator genome reveals conserved architecture of estrogen signaling
Genome Research, 2017Co-Authors: Edward S Rice, Satomi Kohno, John St John, Son Pham, Jonathan M Howard, Liana F Lareau, Brendan Oconnell, Glenn Hickey, Joel Armstrong, Alden DeranAbstract:The American Alligator, Alligator mississippiensis, like all crocodilians, has temperature-dependent sex determination, in which the sex of an embryo is determined by the incubation temperature of the egg during a critical period of development. The lack of genetic differences between male and female Alligators leaves open the question of how the genes responsible for sex determination and differentiation are regulated. Insight into this question comes from the fact that exposing an embryo incubated at male-producing temperature to estrogen causes it to develop ovaries. Because estrogen response elements are known to regulate genes over long distances, a contiguous genome assembly is crucial for predicting and understanding their impact. We present an improved assembly of the American Alligator genome, scaffolded with in vitro proximity ligation (Chicago) data. We use this assembly to scaffold two other crocodilian genomes based on synteny. We perform RNA sequencing of tissues from American Alligator embryos to find genes that are differentially expressed between embryos incubated at male- versus female-producing temperature. Finally, we use the improved contiguity of our assembly along with the current model of CTCF-mediated chromatin looping to predict regions of the genome likely to contain estrogen-responsive genes. We find that these regions are significantly enriched for genes with female-biased expression in developing gonads after the critical period during which sex is determined by incubation temperature. We thus conclude that estrogen signaling is a major driver of female-biased gene expression in the post-temperature sensitive period gonads.
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trpv4 associates environmental temperature and sex determination in the american Alligator
Scientific Reports, 2016Co-Authors: Ryohei Yatsu, Yukiko Ogino, Satomi Kohno, Shinichi Miyagawa, Shigeru Saito, Russell H LowersAbstract:Temperature-dependent sex determination (TSD), commonly found among reptiles, is a sex determination mode in which the incubation temperature during a critical temperature sensitive period (TSP) determines sexual fate of the individual rather than the individual’s genotypic background. In the American Alligator (Alligator mississippiensis), eggs incubated during the TSP at 33 °C (male producing temperature: MPT) yields male offspring, whereas incubation temperatures below 30 °C (female producing temperature: FPT) lead to female offspring. However, many of the details of the underlying molecular mechanism remains elusive and the molecular link between environmental temperature and sex determination pathway is yet to be elucidated. Here we show the Alligator TRPV4 ortholog (AmTRPV4) to be activated at temperatures proximate to the TSD-related temperature in Alligators and using pharmacological exposure, we show that AmTRPV4 channel activity affects gene expression patterns associated with male differentiation. This is the first experimental demonstration of a link between a well-described thermo-sensory mechanism, TRPV4 channel and its potential role in regulation of TSD in vertebrates, shedding unique new light on the elusive TSD molecular mechanism.
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identification and characterization of the androgen receptor from the american Alligator Alligator mississippiensis
Endocrinology, 2015Co-Authors: Shinichi Miyagawa, Brenna M Doheny, Ryohei Yatsu, Yukiko Ogino, Yoshinao Katsu, Satomi Kohno, Louis J Guillette, Hiroshi Ishibashi, Yasuhiko Ohta, Taisen IguchiAbstract:Androgens are essential for the development, reproduction, and health throughout the life span of vertebrates, particularly during the initiation and maintenance of male sexual characteristics. Androgen signaling is mediated by the androgen receptor (AR), a member of the steroid nuclear receptor superfamily. Mounting evidence suggests that environmental factors, such as exogenous hormones or contaminants that mimic hormones, can disrupt endocrine signaling and function. The American Alligator (Alligator mississippiensis), a unique model for ecological research in that it exhibits environment-dependent sex determination, is oviparous and long lived. Alligators from a contaminated environment exhibit low reproductive success and morphological disorders of the testis and phallus in neonates and juveniles, both associated with androgen signaling; thus, the alterations are hypothesized to be related to disrupted androgen signaling. However, this line of research has been limited because of a lack of informatio...
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altered gonadal expression of tgf β superfamily signaling factors in environmental contaminant exposed juvenile Alligators
The Journal of Steroid Biochemistry and Molecular Biology, 2011Co-Authors: Brandon C Moore, Yoshinao Katsu, Satomi Kohno, Louis J Guillette, Taisen Iguchi, Matthew R Milnes, Teresa K WoodruffAbstract:Abstract Environmental contaminant exposure can influence gonadal steroid signaling milieus; however, little research has investigated the vulnerability of non-steroidal signaling pathways in the gonads. Here we use American Alligators (Alligator mississippiensis) hatched from field-collected eggs to analyze gonadal mRNA transcript levels of the activin–inhibin–follistatin gene expression network and growth differentiation factor 9. The eggs were collected from Lake Woodruff National Wildlife Refuge, a site with minimal anthropogenic influence, and Lake Apopka, a highly contaminated lake adjacent to a former EPA Superfund site. The hatchling Alligators were raised for 13 months under controlled conditions, thus limiting differences to embryonic origins. Our data reveal sexually dimorphic mRNA expression in 13-month-old Alligator gonads similar to patterns established in vertebrates with genetic sex determination. In addition, we observed a relationship between lake of origin and mRNA expression of activin/inhibin subunits α and βB, follistatin, and growth differentiation factor 9. Our study suggests that embryonic exposure to environmental contaminants can affect future non-steroidal signaling patterns in the gonads of a long-lived species.
C G Farmer - One of the best experts on this subject based on the ideXlab platform.
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anatomy ontogeny and evolution of the archosaurian respiratory system a case study on Alligator mississippiensis and struthio camelus
Journal of Anatomy, 2020Co-Authors: Emma R. Schachner, John R. Hutchinson, Brandon P Hedrick, Heather A Richbourg, C G FarmerAbstract:The avian lung is highly specialized and is both functionally and morphologically distinct from that of their closest extant relatives, the crocodilians. It is highly partitioned, with a unidirectionally ventilated and immobilized gas-exchanging lung, and functionally decoupled, compliant, poorly vascularized ventilatory air-sacs. To understand the evolutionary history of the archosaurian respiratory system, it is essential to determine which anatomical characteristics are shared between birds and crocodilians and the role these shared traits play in their respective respiratory biology. To begin to address this larger question, we examined the anatomy of the lung and bronchial tree of 10 American Alligators (Alligator mississippiensis) and 11 ostriches (Struthio camelus) across an ontogenetic series using traditional and micro-computed tomography (µCT), three-dimensional (3D) digital models, and morphometry. Intraspecific variation and left to right asymmetry were present in certain aspects of the bronchial tree of both taxa but was particularly evident in the cardiac (medial) region of the lungs of Alligators and the caudal aspect of the bronchial tree in both species. The cross-sectional area of the primary bronchus at the level of the major secondary airways and cross-sectional area of ostia scaled either isometrically or negatively allometrically in Alligators and isometrically or positively allometrically in ostriches with respect to body mass. Of 15 lung metrics, five were significantly different between the Alligator and ostrich, suggesting that these aspects of the lung are more interspecifically plastic in archosaurs. One metric, the distances between the carina and each of the major secondary airways, had minimal intraspecific or ontogenetic variation in both Alligators and ostriches, and thus may be a conserved trait in both taxa. In contrast to previous descriptions, the 3D digital models and CT scan data demonstrate that the pulmonary diverticula pneumatize the axial skeleton of the ostrich directly from the gas-exchanging pulmonary tissues instead of the air sacs. Global and specific comparisons between the bronchial topography of the Alligator and ostrich reveal multiple possible homologies, suggesting that certain structural aspects of the bronchial tree are likely conserved across Archosauria, and may have been present in the ancestral archosaurian lung.
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the pulmonary anatomy of Alligator mississippiensis and its similarity to the avian respiratory system
Anatomical Record-advances in Integrative Anatomy and Evolutionary Biology, 2012Co-Authors: Kent R Sanders, C G FarmerAbstract:Using gross dissections and computed tomography we studied the lungs of juvenile American Alligators (Alligator mississippiensis). Our findings indicate that both the external and internal morphology of the lungs is strikingly similar to the embryonic avian respiratory system (lungs + air sacs). We identified bronchi that we propose are homologous to the avian ventrobronchi (entobronchi), laterobronchi, dorsobronchi (ectobronchi), as well as regions of the lung hypothesized to be homologous to the cervical, interclavicular, anterior thoracic, posterior thoracic, and abdominal air sacs. Furthermore, we suggest that many of the features that Alligators and birds share are homologous and that some of these features are important to the aerodynamic valve mechanism and are likely plesiomorphic for Archosauria. Anat Rec, 2012. © 2012 Wiley Periodicals Inc.
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subglottal pressure and fundamental frequency control in contact calls of juvenile Alligator mississippiensis
The Journal of Experimental Biology, 2011Co-Authors: Tobias Riede, Isao T Tokuda, C G FarmerAbstract:Vocalization is rare among non-avian reptiles, with the exception of the crocodilians, the sister taxon of birds. Crocodilians have a complex vocal repertoire. Their vocal and respiratory system is not well understood but appears to consist of a combination of features that are also found in the extremely vocal avian and mammalian taxa. Anatomical studies suggest that the Alligator larynx is able to abduct and adduct the vocal folds, but not to elongate or shorten them, and is therefore lacking a key regulator of frequency, yet Alligators can modulate fundamental frequency remarkably well. We investigated the morphological and physiological features of sound production in Alligators. Vocal fold length scales isometrically across a wide range of Alligator body sizes. The relationship between fundamental frequency and subglottal pressure is significant in some individuals at some isolated points, such as call onset and position of maximum fundamental frequency. The relationship is not consistent over large segments of the call. Fundamental frequency can change faster than expected by pressure changes alone, suggesting an active motor pattern controls frequency and is intrinsic to the larynx. We utilized a two-mass vocal fold model to test whether abduction and adduction could generate this motor pattern. The fine-tuned interplay between subglottal pressure and glottal adduction can achieve frequency modulations much larger than those resulting from subglottal pressure variations alone and of similar magnitude, as observed in Alligator calls. We conclude that the Alligator larynx represents a sound source with only two control parameters (subglottal pressure and vocal fold adduction) in contrast to the mammalian larynx in which three parameters can be altered to modulate frequency (subglottal pressure, vocal fold adduction and length/tension).
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structure and function of the esophagus of the american Alligator Alligator mississippiensis
The Journal of Experimental Biology, 2005Co-Authors: T J Uriona, J Dazely, F Clayton, C G Farmer, J. MooreAbstract:Esophageal structure and function were studied in juvenile American Alligators (Alligator mississippiensis). The anatomy of Alligators differs from humans in several important aspects: the crocodilian esophagus is more muscular and is composed entirely of smooth muscle. Functionally, the crocodilian esophagus is similar to that of mammals, but Alligators have peak esophageal peristaltic pressures that are 2‐3-fold greater than pressures in the human esophagus. As is found in humans, the incidence of esophageal reflux increased in postprandial animals compared with the fasting state. We observed a large increase in pressure in the lower esophageal sphincter (LES) during ventilation that ranged from 200% to 3000% of the pressures measured during apnea. These pressure changes appear to be intrinsic to the LES. Alligators lack a mammalian-type diaphragm; thus, there is no crural diaphragmatic contribution to LES pressure. These features recommend the Alligator as a useful model for the study of regulation of the LES. Summary
