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At least 451 records · Page 25Linked to original sources
PubMed2001

Differences in protein expression in the subcommissural organ of normal and lordotic lizards (Agama impalearis).

Lordosis, a skeletal malformation, is characterized by abnormal curvature of the vertebral column. Involvement of the subcommissural organ (SCO) in the correct development of the axial skeleton via the thread-like Reissner's fiber (RF) has been suggested. However, the functional significance of the SCO and RF in these mechanisms remains, to date, little understood. To detect eventual changes in the SCO of reptiles bearing a naturally occurring skeletal malformation, we aimed here at investigating with immunohistochemistry RF glycoprotein and immediate early gene expression in the SCO of normal and lordotic lizards. In normal lizards, RF immunoreactivity was evident in the apical and basal domains of SCO cells. In specimens derived from lordotic animals, RF-immunoreactive material filled all SCO cell portions, and numerous large droplets were observed in the basal part of the organ. Cell nuclei exhibiting immunoreactivity to the protein product of the gene c-fos were evident in basal SCO cells of lordotic animals, whereas Fos immunoreactivity was absent in the SCO of normal lizards. The changes detected in RF immunoreactivity and Fos induction in SCO cells of lordotic animals favor the occurrence of changes in the secretory activity and gene expression of SCO cells. The present data further demonstrate modifications occurring in the SCO secretory material in skeletal malformed vertebrates, and support a relationship of such changes with the malformed state of these animals.

Animals↗
PubMed2000

Androgenic regulation of steroid hormone receptor mRNAs in the brain of whiptail lizards.

Sex and species differences in androgenic regulation of steroid hormone receptor mRNAs were examined in the diencephalon of two species of whiptail lizards: Cnemidophorus inornatus is a sexual species and the direct evolutionary ancestor to Cnemidophorus uniparens, an all-female parthenogenetic species. Lizards were gonadectomized and treated with different doses of either aromatizable testosterone or nonaromatizable dihydrotestosterone. The relative abundances of androgen-, oestrogen-, and progesterone-receptor mRNAs were compared in various nuclei following in situ hybridization with homologous riboprobes. A diversity of patterns in androgenic regulation was observed, with effects differing according to brain region, the steroid-receptor mRNA being considered and, in some cases, between androgens. In the ancestral sexual species, intact males had lower androgen-receptor mRNA abundances than castrated, blank-implanted males in the medial preoptic area. Testosterone significantly decreased androgen-receptor mRNA abundance in the medial preoptic area of castrated males. Males had higher androgen-receptor mRNA levels in the preoptic area than females generally and neither the sexual or parthenogenetic females showed a decrease in androgen-receptor mRNA with androgen treatment. Both testosterone and dihydrotestosterone increased oestrogen-receptor mRNA abundance in the ventromedial hypothalamus of C. inornatus, but no sex differences in this effect were observed. Gonadectomy decreased, whereas androgen treatment increased, progesterone-receptor mRNA abundance in the ventromedial hypothalamus. There was a sex difference in this response to androgen in the sexual species, with males having greater amounts than females in this brain area. The parthenogenetic species exhibited a similar pattern to females of the sexual species, but the levels were higher overall, possibly because Cnemidophorus uniparens is triploid. The periventricular preoptic area showed a different pattern, with testosterone treatment increasing progesterone-receptor mRNA abundance in both sexes of the sexual species and in the parthenogenetic species, while dihydrotestosterone did not. The diversity of patterns in androgen effects indicates that gonadal sex, aromatization of androgen, and perhaps gene dosage all influence the expression of steroid-receptor mRNAs in the lizard brain.

Androgens↗
PubMed2003

Identification of circadian brain photoreceptors mediating photic entrainment of behavioural rhythms in lizards.

We have shown previously that in ruin lizards (Podarcis sicula) the ablation of all known photoreceptive structures (lateral eyes, pineal and parietal eye) in the same individual animal does not prevent entrainment of their circadian locomotor rhythms to light. The present study was aimed at identifying the circadian brain photoreceptors mediating entrainment. For this purpose, we looked for opsin expression in the brain by means of immunocytochemistry. Using anti-cone-opsin antiserum CERN 874 we have localized photoreceptors in the periventricular area of hypothalamus, near the third cerebral ventricle. We also cloned a brain opsin cDNA that, on the basis of the deduced amino acid sequence, appears to belong to the RH2 class of cone-opsins. We named the cloned cone-opsin Ps-RH2. To examine whether brain cone-opsins mediate photic entrainment of circadian locomotor rhythms, we performed post-transcriptional inactivation experiments by injecting an expression eukaryotic vector transcribing the antisense cone-opsin Ps-RH2 mRNA in the third cerebral ventricle of pinealectomized-retinectomized lizards previously entrained to a light-dark (LD) cycle. Injections of the antisense construct abolished photic entrainment of circadian locomotor rhythms of pinealectomized-retinectomized lizards to the LD cycle for 6-9 days. CERN 874 completely failed to label cells within the periventricular area of hypothalamus of brains injected with antisense construct. Thus, abolishment of photic entrainment is due to inactivation of endogenous brain cone-opsins mRNA. The present results demonstrate for the first time in a vertebrate that brain cone-opsins are part of a true circadian brain photoreceptor participating in photic entrainment of behavioural rhythms.

Amino Acid Sequence↗
PubMed1992

Heat shock proteins and thermoresistance in lizards.

The synthesis of heat shock proteins (hsps) at normal physiological and elevated temperatures has been correlated with the natural adaptation of an organism to heat in nine lizard species studied. These species differ drastically by their adaptation to elevated temperature and represent a spectrum of forms isolated from various geographical regions of the Union of Soviet Socialist Republics. The synthesis of hsps belonging to the hsp70 family and their correspondent mRNAs have been compared at different temperature regimes. This analysis has shown that lizards inhabiting the Middle Asia deserts are characterized by a higher content of hsp70-like proteins at normal physiological temperatures (2- to 5-fold differences) when compared with the forms from central and northern regions of the European part of the Union of Soviet Socialistic Republics. Analysis of hsp70 mRNA at different temperatures substantiated these observations, showing evident correlation between adaptation of a given form to hyperthermia and the quantity of hsp70 mRNA in the cells under non-heat-shock conditions. The results obtained with a wide spectrum of ecologically different lizard species, coupled with other relevant data, enable us to propose a general rule applicable to poikilothermic organisms. This rule postulates the direct correlation between the characteristic temperature of the ecological niche of a given species and the amount of hsp70-like proteins in the cells at normal temperature.

Animals↗
PubMed2002

Fine structure of the external nasal gland of two lizards (Podarcis sicula campestris and Chalcides chalcides).

In this study, we describe the ultrastructural features of the external nasal gland in two lizards: ruin lizard (Podarcis sicula campestris) and seps (Chalcides chalcides). Two secretory cell types, which differ interspecifically, have been found in the secretory endpieces of the glandular tubules in both species examined. An unusual morphological observation was the presence of paracrystalline structures in the secretory granules of the seromucous cells of the external nasal gland of the seps. These structures may be related to the packaging mechanism of glycoproteins or to their macromolecular structure. They may also reflect segregation of heterogeneous subcomponents within the same secretory granule. The striated cells are located in the distal segment of the glandular tubules, and have the typical ultrastructural features of the cells which in some species of reptiles, but not in these two lizards, are known to be capable of elaborating a hyperosmotic saline solution.

Animals↗
PubMed2005

Gastrointestinal helminths of the lizard Chalcides ocellatus from Benghazi, Libya.

Chalcides ocellatus, a scincid lizard, sampled during October 1998 to December 1999 from Benina (farmland) and Al-Kueffia (a rocky area) in Benghazi, Libya, was found to harbour three intestinal nematodes, Pharyngodon mamillatus, Thelandros alatus and Parapharyngodon micipsae, and an intestinal cestode, Oochoristica tuberculata. Thelandros alatus, P. micipsae and O. tuberculata were recorded for the first time in C. ocellatus. Parapharyngodon micipsae was detected in C. ocellatus from Benina and O. tuberculata from lizards in Al-Kueffia. The majority (87.6%) of C. ocellatus were infected with helminth parasites and the levels of infection were higher in males than in females but this difference was not significant. Pharyngodon mamillatus recorded the highest number of nematode parasites in C. ocellatus, although there was no relationship between the number of nematode parasites recovered and host density. In lizards infected with the cestode O. tuberculata, males had shorter snout-vent lengths than females. From a total of 153 C. ocellatus, 120 (78.4%) showed single and 14 (9.2%) showed mixed parasitic infections. Mixed infections between different species of nematodes were not observed.

Animals↗
PubMed2000

Phylogenetic relationships among the phrynosomatid sand lizards inferred from mitochondrial DNA sequences generated by heterogeneous evolutionary processes.

Nucleotide sequences of the mitochondrial protein coding cytochrome b (cyt b; 650 bp) and small-subunit 12S ribosomal RNA (approximately 350 bp) genes were used in analyses of phylogenetic relationships among extant phrynosomatid sand lizards, including an examination of competing hypotheses regarding the evolution of "earlessness." Sequences were obtained from all currently recognized species of sand lizards as well as representatives of the first and second outgroups and analyzed using both parsimony and likelihood methods. The cyt b data offer strong support for relationships that correspond with relatively recent divergences and moderate to low support for relationships reflecting more ancient divergences within the clade. These data support monophyly of the "earless" taxa, the placement of Uma as the sister taxon to the other sand lizards, and monophyly of all four taxa traditionally ranked as genera. All well-supported relationships in the 12S phylogeny are completely congruent with well-supported relationships in the cyt b phylogeny; however, the 12S data alone provide very little support for deeper divergences. Phylogenetic relationships within species are concordant with geography and suggest patterns of phylogeographic differentiation, including the conclusion that at least one currently recognized species (Holbrookia maculata) actually consists of more than one species. By independently optimizing likelihood model parameters for various subsets of the data, we found that nucleotide substitution processes vary widely between genes and among the structural and functional regions or classes of sites within each gene. Therefore, we compared competing phylogenetic hypotheses, using parameter estimates specific to those subsets, analyzing the subsets separately and in various combinations. The hypothesis supported by the cyt b data was favored over rival hypotheses in all but one of the five comparisons made with the entire data set, including the set of partitions that best explained the data, although we were unable to confidently reject (P < 0.05) alternative hypotheses. Our results highlight the importance of optimizing models and parameter estimates for different genes or parts thereof--a strategy that takes advantages of the strengths of both combining and partitioning data.

Animals↗
PubMed2004

Purification and characterization of liver lectins from a lizard, Sceloporus spinosus.

This study discusses the purification of soluble beta-galactose lectins obtained from the lizard liver of Sceloporus spinosus. The first lectin named lizard hepatic lectin-1 (LHL-1) presented a molecular weight of 31,750, with an isoelectric point of 4.25. The highest specific hemagglutinating activity was achieved using human blood type A1: N-acetylgalactosamine (GalNAc)-galactose (Gal)-fucose (Fuc). Carbohydrate inhibition assays indicated a higher lectin specificity for GalNAc. For LHL-2 the molecular weight obtained was 23,850 with an isoelectric point of 3.25. The highest carbohydrate specificity was observed for Gal. These lizard hepatic lectins are similar to the mammal hepatic lectins previously reported. However, it is different from the alligator hepatic lectin (AHL). The homology analyses of LHL-1 resulted in 100% identity with the Steroidogenic acute regulatory protein (StAR), while LHL-2 was similar to adenylate kinase (75% identity). We suggest that these liver lectins are related to the inherent functions of liver previously reported.

ABO Blood-Group System↗
PubMedDate not supplied

Ontogeny of the pulmonary surfactant and antioxidant enzyme systems in the viviparous lizard, Tiliqua rugosa.

The antioxidant enzyme (AOE) system protects the lung from oxidative damage. The pulmonary surfactant (PS) system lowers the interfacial pressure within the lung, improving lung compliance and aiding lung clearance. In mammals, the AOE and PS systems develop in tandem during the final 10%-20% of gestation. Here, we investigated the development of these systems in the viviparous skink, Tiliqua rugosa. The content of total phospholipid (PL), disaturated phospholipid (DSP), and cholesterol (Chol) increased in lung washings from foetal lizards with advancing gestational age. Similarly, the relative saturation of the PLs increased throughout gestation, with mid-stage 40 foetuses having a DSP/PL equivalent to newborns and adults. Maternal lizards had significantly less total PL, DSP, and Chol than nongravid and newborn lizards; however, the relative composition did not differ from nongravid animals. This presumably results from compression of the lungs under the bulk of the developing foetus. The Chol/PL and Chol/DSP ratios declined early in development such that mid-stage 40 embryos had comparable ratios to both newborns and adults. Thus, it appears that the PS system matures in a similar manner in skinks and in mammals. However, the composition of surfactant is complete some weeks before parturition, probably to enable improved survivorship of the precocial young in the event of premature birth. Unlike the surfactant lipids, the AOEs, catalase, superoxide dismutase, and glutathione peroxidase did not differ appreciably throughout gestation. It appears therefore that like the surfactant lipids the AOE system is in readiness for air breathing throughout the latter stages of gestation, possibly in preparation for premature birth. Unlike mammals, the PS and AOE systems develop independently from one another.

Age Factors↗
PubMedDate not supplied

Sex-based differences and similarities in locomotor performance, thermal preferences, and escape behaviour in the lizard Platysaurus intermedius wilhelmi.

Differences between sexes in physiological performance have received little attention in animals. We tested for sex differences in maximum sprint speed and maximal exertion over a range of temperatures in a population of Platysaurus intermedius wilhelmi lizards. We also examined sex-based differences in selected temperature range, mean field body temperatures (T(b)), and thermal activity limits. Finally, we conducted field studies to quantify male and female responses to a potential predator, which may be affected by their respective performance capabilities. Males were faster than females at all temperatures, and body size had no significant effect on sprint speeds. Males and females also selected similar T(b)'s when placed in a thermal gradient, but in the field, male lizards' T(b)'s were different from those of the females. However, predicted sprint speeds for males and females at their field T(b)'s are similar. No significant differences were found between males and females with regard to maximal exertion. When approached in the field, adult male lizards took refuge significantly earlier than did adult females and also fled over shorter distances, suggesting that females rely on crypsis as an escape strategy.

Analysis of Variance↗
PubMed2005

The cost of living large: comparative gliding performance in flying lizards (Agamidae: Draco).

Despite exhibiting considerable interspecific variation in body mass, flying lizards of the genus Draco are isometric in their area-mass scaling relationships and exhibit no significant compensatory variation in wing aspect ratio. Thus, larger species are expected to be relatively poor gliders, in lieu of behavioral or physiological compensation, when compared with smaller congeners. Here we tested this hypothesis by conducting gliding performance trials for 11 Draco species spanning virtually the entire size range of the genus. We considered three primary performance variables: maximum velocity adjusted for wind conditions, height lost over a standard horizontal glide distance, and glide angle. Comparative analysis confirmed that larger species are relatively poor gliders and do not compensate substantially for their higher wing loadings via either behavioral or physiological mechanisms. Flying lizards were found to exhibit substantial context-dependent variation in glide performance, with smaller species often exhibiting extensive variation in height lost and glide angle between trials. Variation also was observed in empirically derived velocity profiles, with only a subset of individuals appearing to perform equilibrium glides. Such size-dependent variation in performance has important consequences for the ecology and evolution of flying lizards and other glissant taxa.

Animals↗
PubMedDate not supplied

Evolution of viviparity in sceloporine lizards: in utero PO2 as a developmental constraint during egg retention.

Reptilian viviparity evolves through selection for increasingly prolonged egg retention within the oviduct. In the majority of sceloporine lizard species, however, egg retention past the normal time of oviposition results in retarded or arrested embryonic development. In this study, we tested the hypothesis that the amount of embryonic development normally attained in utero is directly related to in utero oxygen partial pressure (PO(2)). The three species of sceloporine lizards we used are characterized by developmental arrest (Urosaurus ornatus), retarded development (Sceloporus virgatus), and normal development (Sceloporus scalaris) when eggs are retained. We incubated eggs of these species for 10 d under conditions that simulated retention in the oviduct at a range of experimental oxygen partial pressures (PO(2)). We estimated in utero PO(2) from a standard curve generated from the stage and dry mass of experimental embryos incubated for 10 d at known PO(2). The standard curve was then used to predict the PO(2) associated with the observed rate of development of embryos retained in utero. The results of this study showed that the degree of embryonic development attained in utero during egg retention was positively associated with in utero PO(2). The results indicate that oxygen availability in utero is associated with interspecific differences in the capacity to support intrauterine development in sceloporine lizards.

Animals↗
PubMed2006

Daily patterns of metabolic rate among New Zealand lizards (Reptilia: Lacertilia: Diplodactylidae and Scincidae).

In addition to the effects of temperature fluctuations on metabolic rate, entrained endogenous rhythms in metabolism, which are independent of temperature fluctuations, may be important in overall energy metabolism in ectotherms. Daily entrained endogenous rhythms may serve as energy-conserving mechanisms during an animal's active or inactive phase. However, because nocturnal lizards often take advantage of thermal opportunities during the photophase (light), their daily metabolic rhythms may be less pronounced than those of diurnal species. We measured the rate of oxygen consumption (VO(2)) as an index of metabolic rate of eight temperate lizard species (four nocturnal, three diurnal, and one crepuscular/diurnal; n = 7-14) over 24 h at 13 degrees C and in constant darkness to test whether daily patterns (including amplitude, magnitude, and time of peak VO(2)) of metabolic rate in lizards differ with activity period. We also tested for phylogenetic differences in metabolic rate between skinks and geckos. Three daily patterns were evident: 24-h cycle, 12-h cycle, or no daily cycle. The skink Cyclodina aenea has a 12-h crepuscular pattern of oxygen consumption. In four other species, VO(2) increased with, or in anticipation of, the active part of the day, but three species had rhythms offset from their active phase. Although not correlated with activity period or phylogeny, amplitude of VO(2) may be correlated with whether a species is temperate or tropical. In conclusion, the metabolic rate of many species does not always correlate with the recorded activity period. The dichotomy of ecology and physiology may be clarified by more in-depth studies of species behaviors and activity periods.

Animals↗
PubMed2006

Breathing with big babies: ventilation and oxygen consumption during pregnancy in the lizard Tiliqua rugosa.

We determined the effects of high gestational loads on ventilation and the rate of oxygen consumption (VO2) in the scincid lizard Tiliqua rugosa. Tiliqua rugosa is a large viviparous lizard that gives birth to one to four young after 6-7 mo gestation. Pregnant females gave birth to large young, weighing 89.5+/-5.9 g, which represents 21.6%+/-2.6% of maternal body mass. As the embryos developed, they occupied an increasingly large proportion of the body cavity, decreasing food consumption and compressing the gastrointestinal tract. Computerized axial tomography scans demonstrated that the lungs were compressed and/or regionally collapsed by the developing embryos, potentially compromising ventilation. Both minute ventilation (VE) and tidal volume decreased as gestation progressed, but no compensatory changes in breathing frequency or in the duration of the nonventilatory period were observed. The total rate of VO2, consisting of contributions from both maternal and fetal tissues, did not change during gestation, suggesting that maternal VO2 decreases as fetal VO2 increases. Pregnant females demonstrated a decreased ventilatory response to increased respiratory drive (triggered via inhalation of hypoxic hypercapnic gas), which may be associated with the increased energetic cost of ventilating a compressed lung or the desensitization of chemoreceptors during gestation. The decreased ability of the respiratory system to respond to increased respiratory drive may have important consequences for locomotor performance and predator avoidance in pregnant lizards.

Animals↗
PubMed2000

Description of a monomeric prototype galectin from the lizard Podarcis hispanica.

Galectins are a continuously expanding family of beta-galactoside-binding lectins present in a variety of evolutionarily divergent animal species. Here we report, for the first time, that expression of galectins extends to the reptilia lineage of lizards. Up to five lactose-binding proteins were isolated from the lizard Podarcis hispanica by affinity chromatography on asialofetuin-Sepharose. The main component, which is most abundantly expressed in skin, was purified from this tissue and further characterized. Under native conditions the protein behaved as a monomer with a molecular mass of 14,500 Da and an isoelectric point of 6.3. Based on sequence homology of the 58 N-terminal amino acid residues with galectins, and on its demonstrated galactoside-binding activity, this lectin we named LG-14 (from Lizard Galectin and 14 kDa) is classified as a new member of the galectin family. LG-14 falls into and strengthen the still thinly populated category of monomeric prototype galectins.

Amino Acid Sequence↗
PubMed1990

Survey of birds and lizards for ixodid ticks (Acari) and spirochetal infection in northern California.

A total of 138 birds (24 species) was captured in an oak woodland between December 1988 and June 1989 at the University of California, Sierra Foothill Range Field Station, Yuba County, Calif. Ticks were not found on 71 birds captured between December 1988 and March 1989. Five subadult Ixodes pacificus Cooley & Kohls were removed from 3 of 67 birds caught between April and June 1989. These three birds, an orange-crowned warbler (Vermivora celata (Say], a lazuli bunting (Passerina amoena (Say], and a chipping sparrow (Spizella passerina (Bechstein], represent new host records for I. pacificus in California. Tissues from two ticks and thick blood films prepared from 126 birds tested negative for spirochetes by direct immunofluorescence (DI). A total of 172 larval and 197 nymphal I. pacificus was removed from 15 of 16 western fence lizards (Sceloporus occidentalis Baird & Girard) caught between April and June 1989 in the same location as were birds. Thick blood films prepared from all 16 lizards and tissue smears from 334 of the ticks (143 larvae and 191 nymphs) were DI test-negative for spirochetes. One (1.1%) of 93 adult I. pacificus collected at the bird-lizard capture site in February 1989 was infected with spirochetes that resembled B. burgdorferi.

Animals↗
PubMed1986

Evolution and testosterone content of the epididymis during the annual cycle of the lizard Lacerta vivipara.

The lizard epididymis provides a model for studying the control, by testosterone, of a secretory activity related to the physiology of spermatozoa. To evaluate seasonal changes and to establish chronological correlations between the structure of the epididymis and its testosterone content, lizards (Lacerta vivipara) were killed between March (emergence) and October (retreat). The epididymal tissue was examined histologically and assayed for testosterone content. Ten stages of development were defined, mainly on the basis of the epithelial structure and the morphological features of secretory activity. Degeneration of the epithelium after the breeding period and its subsequent renewal also were considered. Increased epithelial height and secretory activity coincided with a progressive rise of the testosterone level, and a severe atrophy followed a sudden reduction of blood testosterone. Reorganization of the epithelium takes place when testosterone is at its lowest level, and the hormonal dependency of this stage is questionable. This study confirms in vivo, during a sexual cycle, experimental evidence previously obtained concerning testosterone's control of the secretory activity of the lizard epididymis.

Animals↗
PubMed2000

The role of colour in signalling and male choice in the agamid lizard Ctenophorus ornatus.

Bright coloration and complex visual displays are frequent and well described in many lizard families. Reflectance spectrometry which extends into the ultraviolet (UV) allows measurement of such coloration independent of our visual system. We examined the role of colour in signalling and mate choice in the agamid lizard Ctenophorus ornatus. We found that throat reflectance strongly contrasted against the granite background of the lizards' habitat. The throat may act as a signal via the head-bobbing and push-up displays of C. ornatus. Dorsal coloration provided camouflage against the granite background, particularly in females. C. ornatus was sexually dichromatic for all traits examined including throat UV reflectance which is beyond human visual perception. Female throats were highly variable in spectral reflectance and males preferred females with higher throat chroma between 370 and 400 nm. However, female throat UV chroma is strongly correlated to both throat brightness and chest UV chroma and males may choose females on a combination of these colour variables. There was no evidence that female throat or chest coloration was an indicator of female quality. However, female brightness significantly predicted a female's laying date and, thus, may signal receptivity. One function of visual display in this species appears to be intersexual signalling, resulting in male choice of females.

Animals↗