Animal Models

Carroll, R. (2006). Marine adaptation in reptiles: a model for the study of large scale patterns and processes of evolution. Journal of Vertebrate Paleontology 26(3, Suppl. S): 48A. ISSN: 0272-4634.
Descriptors: reptiles, marine adaptation, processes of evolution, study, model, patterns, meeting abstract.
Notes: Meeting Information: 66th Annual Meeting of the Society of Vertebrate Paleontology, Ottawa, Canada; October 18 -21, 2006.

Crews, D. and M.C. Moore (2005). Historical contributions of research on reptiles to behavioral neuroendocrinology. Hormones and Behavior 48(4): 384-394. ISSN: 0018-506X.
NAL Call Number: QP801.H7H64
Abstract: Some of the first experiments in behavioral endocrinology in the 1930s were conducted with lizards, but events led to a hiatus that lasted for 30 years. In the 1960s, research resumed using techniques current at the time, but it was not until the mid-1970s that behavioral neuroendocrinology "discovered" reptiles as animal model systems. This historical review summarizes this period of work, illustrating an enormous increase in research that have led to conclusions such as (1) the phenomenon of dissociated reproductive strategies and hormone-independent behaviors, which have aided our understanding of how the "memory" of sex steroid actions is maintained. (2) Progesterone plays an important role in the organization and activation of sexual behavior in males. Progesterone also synergizes with T to control male courtship much as does estrogen and progesterone to control sexual receptivity in females. Thus, progesterone is as much a "male" hormone as it is a "female" hormone. (3) Use of cytochrome oxidase histochemistry to study the role of experience over the long term in modifying brain activity. (4) Hormone manipulations as a powerful tool to test hypotheses about the evolution of behavior in free-living animals.
Descriptors: lizards, aggression, behavior, neuroendocrinology, reptiles, physiology, gonadal steroid hormones, history, 20th century research, neuroendocrinology methods, reproduction physiology, sex factors, sexual behavior.

Daniels, C.B., B.C. Lewis, C. Tsopelas, S.L. Munns, S. Orgeig, M.E. Baldwin, S.A. Stacker, M.G. Achen, B.E. Chatterton, and R.D. Cooter (2003). Regenerating lizard tails: a new model for investigating lymphangiogenesis. FASEB Journal 17(3): 479-481. ISSN: print: 0892-6638; online: 1530-6860.
NAL Call Number: QH301.F3
Abstract: Impaired lymphatic drainage in human limbs causes the debilitating swelling termed lymphoedema. In mammals, known growth factors involved in the control of lymphangiogenesis (growth of new lymph vessels) are vascular endothelial growth factors-C and -D (VEGF-C/D). Here we characterize a model of lymphangiogenesis in which the tail of lizards is regenerated without becoming oedematous. Three weeks after the tail is shed (autotomy), there are a small number of large diameter lymphatic vessels in the regenerated tail. Thereafter, the number increases and the diameter decreases. A functional lymphatic network, as determined by lymphoscintigraphy, is established 6 wk after autotomy. The new network differs morphologically and functionally from that in original tails. This lymphatic regeneration is associated with an up-regulation of a reptilian homologue of the VEGF-C/D protein family (rVEGF-C/D), as determined by Western blot analysis using a human reactive VEGF-C polyclonal antibody. Regenerating lizard tails are potentially useful models for studying the molecular basis of lymphangiogenesis with a view to developing possible treatments for human lymphoedema.
Descriptors: reptiles, lizard tails, regenerating, new model, investigating, lymphangiogenesis.

Lopez Garcia, C., A. Molowny, J. Nacher, X. Ponsoda, F. Sancho Bielsa, and G. Alonso Llosa (2002). The lizard cerebral cortex as a model to study neuronal regeneration. Anais Da Academia Brasileira De Ciencias 74(1): 85-104. ISSN: print: 0001-3765; online: 1678-2690.
Abstract: The medial cerebral cortex of lizards, an area homologous to the hippocampal fascia dentata, shows delayed postnatal neurogenesis, i.e., cells in the medial cortex ependyma proliferate and give rise to immature neurons, which migrate to the cell layer. There, recruited neurons differentiate and give rise to zinc containing axons directed to the rest of cortical areas, thus resulting in a continuous growth of the medial cortex and its zinc-enriched axonal projection. This happens along the lizard life span, even in adult lizards, thus allowing one of their most important characteristics: neuronal regeneration. Experiments in our laboratory have shown that chemical lesion of the medial cortex (affecting up to 95% of its neurons) results in a cascade of events: first, massive neuronal death and axonal-dendritic retraction and, secondly, triggered ependymal-neuroblast proliferation and subsequent neo-histogenesis and regeneration of an almost new medial cortex, indistinguishable from a normal undamaged one. This is the only case to our knowledge of the regeneration of an amniote central nervous centre by new neuron production and neo-histogenesis. Thus the lizard cerebral cortex is a good model to study neuronal regeneration and the complex factors that regulate its neurogenetic, migratory and neo-synaptogenetic events.
Descriptors: reptiles, lizards, cerebral cortex physiology, nerve regeneration, neurons physiology, cerebral cortex cytology, animal models.

Talent, L.G., J.N. Dumont, J.A. Bantle, D.M. Janz, and S.G. Talent (2002). Evaluation of western fence lizards (Sceloporus occidentalis) and eastern fence lizards (Sceloporus undulatus) as laboratory reptile models for toxicological investigations. Environmental Toxicology and Chemistry 21(5): 899-905. ISSN: 0730-7268.
NAL Call Number: QH545.A1E58
Abstract: A need is recognized for one or more laboratory reptile models for use in ecotoxicological studies and risk assessments. Maintenance of breeding populations of most reptile species under laboratory conditions is not practical because of their size and slow maturation rate. However, a number of species of spiny lizards (Sceloporus sp.) are small, mature quickly, and reproduce under laboratory conditions. We evaluated three populations of western fence lizards (S. occidentalis) and four populations of eastern fence lizards (S. undulatus) for their performance under laboratory conditions. We reared an F1 generation of each population and compared their performance relative to survival, growth, maturation rate, and reproductive output. A population from the San Joaquin Valley (CA. USA) performed especially well under laboratory conditions and is a good candidate for a laboratory model. We also examined the sensitivity of developing fence lizard embryos to an estrogenic chemical to determine if male secondary sex characteristics were affected. Microinjecting eggs with an estrogenic chemical (17alpha-ethinylestradiol) feminized males and prevented development of embryonic secondary sex characteristics. Therefore, embryonic fence lizards may be useful for studying the effects of endocrine-disrupting chemicals.
Descriptors: reptiles, fence lizards, Sceloporus occidentalis, Sceloporus undulatus, laboratory reptile models, toxicological investigations, pollution, evaluation, risk assessment, embryonic fence lizards.

Vallone, D., E. Frigato, C. Vernesi, A. Foa, N.S. Foulkes, and C. Bertolucci (2007). Hypothermia modulates circadian clock gene expression in lizard peripheral tissues. American Journal of Physiology. Regulatory, Integrative and Comparative Physiology 292(1): R160-R166. ISSN: print: 0363-6119; online: 1422-1490.
Online: http://dx.doi.org/10.1152/ajpregu.00370.2006
Abstract: The molecular mechanisms whereby the circadian clock responds to temperature changes are poorly understood. The ruin lizard Podarcis sicula has historically proven to be a valuable vertebrate model for exploring the influence of temperature on circadian physiology. It is an ectotherm that naturally experiences an impressive range of temperatures during the course of the year. However, no tools have been available to dissect the molecular basis of the clock in this organism. Here, we report the cloning of three lizard clock gene homologs (Period2, Cryptochrome1, and Clock) that have a close phylogenetic relationship with avian clock genes. These genes are expressed in many tissues and show a rhythmic expression profile at 29 degrees C in light-dark and constant darkness lighting conditions, with phases comparable to their mammalian and avian counterparts. Interestingly, we show that at low temperatures (6 degrees C), cycling clock gene expression is attenuated in peripheral clocks with a characteristic increase in basal expression levels. We speculate that this represents a conserved vertebrate clock gene response to low temperatures. Furthermore, these results bring new insight into the issue of whether circadian clock function is compatible with hypothermia.
Descriptors: reptiles, lizard, Podarcis sicula, circadian clock, hypothermia, modulates, gene expression, peripheral tissues, temperature changes.