Distribution of arginine vasotocin in the brain of the lizard Anolis carolinensis

Summary The distribution of immunoreactive arginine vasotocin (AVT-ir) was determined in the brain of the lizard Anolis carolinensis. Cells and fibers containing AVT-ir were found in the medial septal region, lamina terminalis, lateral forebrain bundle, preoptic area, supraoptic nucleus, anterior hypothalamus, paraventricular nucleus, periventricular nucleus, arcuate nucleus, and ventromedial nucleus of the thalamus. Occasional AVT-ir cells were found in the interpeduncular nucleus. Fibers containing AVT-ir were found in the cortex, around the olfactory ventricle, in the diagonal band of Broca, amygdala area, dorsal ventricular ridge, striatum, nucleus accumbens, septum, ventromedial hypothalamus, lateral hypothalamus, medial forebrain bundle, median eminence, pars nervosa, nucleus of the solitary tract, locus coeruleus, cerebellar cortex (granular layer), dorsal part of the nucleus of the lateral lemniscus, substantia nigra, and myelencephalon. The intensity of AVT-ir staining was, in general, greater in males than in females. Comparison of AVT-ir distribution in A. carolinensis with those previously published for other reptilian species revealed species-specific differences in distribution of AVT.     

Hormones, sexual signals, and performance of green anole lizards (Anolis carolinensis)

The evolutionary processes that result in reliable links between male signals and fighting capacity have received a great deal of attention, but the proximate mechanisms underlying such connections remain understudied. We studied a large sample of male green anole lizards (Anolis carolinensis) to determine whether testosterone or corticosterone predicted dewlap size and/or bite-force capacity, as dewlap size is known to be a reliable predictor of bite-force capacity in territorial males. We also examined whether these relationships were consistent between previously described body size classes ("lightweights" and "heavyweights"). Heavyweights had 50% higher testosterone concentrations than lightweights during the breeding season, suggesting a mechanism for the disproportionately larger heads and dewlaps and higher bite-forces of heavyweights. Plasma testosterone concentrations were positively correlated with dewlap size and bite-force performance in lightweights (but not heavyweights) but only because of mutual intercorrelation of all three variables with body size. We suggest two possibilities for the relationship between testosterone levels and body size: (1) testosterone promotes growth in this species or (2) smaller sexually mature males are unable to compete with larger males such that the benefits of elevated testosterone do not outweigh the costs. Corticosterone levels did not differ between the male morphs, and lightweights, but not heavyweights, showed an inverse relationship between testosterone levels and corticosterone levels. Our results suggest that testosterone is important for traits related to dominance in adult male green anoles and may influence the ability to compete with rivals via fighting ability or through the use of signals.     

Dynamics and mechanics of social rank reversal

Stable social relationships are rearranged over time as resources such as favored territorial positions change. We test the hypotheses that social rank relationships are relatively stable, and although social signals influence aggression and rank, they are not as important as memory of an opponent. In addition, we hypothesize that eyespots, aggression and corticosterone influence serotonin and N-methyl-D-aspartate (NMDA) systems in limbic structures involved in learning and memory. In stable adult dominant-subordinate relationships in the lizard Anolis carolinensis, social rank can be reversed by pharmacological elevation of limbic serotonergic activity. Any pair of specific experiences: behaving aggressively, viewing aggression or perceiving sign stimuli indicative of dominant rank also elevate serotonergic activity. Differences in the extent of serotonergic activation may be a discriminating and consolidating factor in attaining superior rank. For instance, socially aggressive encounters lead to increases in plasma corticosterone that stimulate both serotonergic activity and expression of the NMDA receptor subunit 2B (NR_2B) within the CA₃ region of the lizard hippocampus. Integration of these systems will regulate opponent recognition and memory, motivation to attack or retreat, and behavioral and physiological reactions to stressful social interactions. Contextually appropriate social responses provide a modifiable basis for coping with the flexibility of social relationships.     

Heterogeneity of astrocytic membranes in the optic nerve and spinal cord of the lizard,Anolis carolinensis

Summary The architecture of astrocytic membranes in the optic nerve and the spinal cord of the lizard, Anolis carolinensis, was investigated by use of the freeze-fracturing technique. Whereas astrocytes in mammals reveal so-called orthogonal arrays of particles (OAPs) in their membranes, astrocytes in lower vertebrates lack these structures. This study demonstrates for the first time OAPs in astrocytes from a submammalian species. They were found commonly in the optic nerve and less frequently in the spinal cord. However, the OAPs in astrocytes of spinal cord were confined to midtrunk levels; the astrocytes in the caudal spinal cord failed to reveal OAPs.Additionally, the ependymal cells around the central canal did not show any OAPs, either in the thoracic or in the caudal spinal cord. They were interconnected by gap and tight junctions, which were not intercalated with each other.The findings support our current working hypothesis according to which the presence and absence of OAPs in astrocytes may be correlated with regenerative incapability or capability of CNS-structures; i.e., whereas the thoracic spinal cord in Anolis carolinensis is known to be incapable of regeneration after injury, the caudal spinal cord is regenerative.     

Catecholaminergic cells and fibers in the brain of the lizard Anolis carolinensis identified by traditional as well as whole-mount immunohistochemistry

Summary Using traditional as well as whole-mount immunohistochemistry, we described the location of tyrosine hydroxylase-and dopamine beta hydroxylase-positive cells and fibers in the brain of the lizard Anolis carolinensis. Major catecholaminergic cell groups were in the ependyma in certain ventricular regions, alous coeruleus, anterior hypothalamic and lateral hypothalamic areas, and in the mesencephalic tegmental region, locus coeruleus, nucleus of the solitary tract, vagal motor nucleus, and rhombencephalic reticular formation. Major catecholaminergic fibers, tracts and varicosities included tuberohypophysial, mesolimbic, nigrostriatal, isthmocortical, medullohypothalamic, and coeruleospinal systems. Although the catecholaminergic systems in A. carolinensis are similar to those in the brains of other lizards studied, there are a few species differences. Our information about A. carolinensis will be used to help localize the hypothalamic asymmetry in catecholamine metabolism previously described in this lizard.     

Effect of gestation temperature on sexual and morphological phenotypes of offspring in a viviparous lizard, Eremias multiocellata

It has been documented in some reptiles that thermal environment can induce variation in sex ratio and morphological phenotypes of offspring. Here, the viviparous lizards (Eremias multiocellata) were maintained under different temperatures during pregnancy to test the effects of this treatment on sexual and morphological phenotypes of offspring, and to investigate whether this lizard is subject to temperature-dependent sex determination (TSD). The warmer temperatures resulted in shorter gestation periods and a higher ratio of male: female births; however, gestation temperature did not affect the neonates’ body mass or snout–vent length (SVL). The gestation temperatures also had significant effects on the mean litter size. Therefore, our results show that the viviparous lizard E. multiocellata might be a TSD species, providing the mothers the opportunity to manipulate the sex ratio of their offspring.     

Relative clonal proportions over time in mixed-genotype infections of the lizard malaria parasite Plasmodium mexicanum

Vertebrate hosts of malaria parasites (Plasmodium) often harbour two or more genetically distinct clones of a single species, and interaction among these co-existing clones can play an important role in Plasmodium biology. However, how relative clonal proportions vary over time in a host is still poorly known. Experimental mixed-clone infections of the lizard malaria parasite, Plasmodium mexicanum, were followed in its natural host, the western fence lizard using microsatellite markers to determine the relative proportions of two to five co-existing clones over time (2-3 months). Results for two markers, and two PCR primer pairs for one of those, matched very closely, supporting the efficacy of the method. Of the 54 infections, 67% displayed stable relative clonal proportions, with the others showing a shift in proportions, usually with one clone outpacing the others. Infections with rapidly increasing or slowly increasing parasitemia were stable, showing that all clones within these infections reproduced at the same rapid or slow rate. Replicate infections containing the same clones did not always reveal the same growth rate, final parasitemia or dominant clone; thus there was no clone effect for these life history measures. The rate of increase in parasitemia was not associated with stable versus unstable relative proportions, but infections with four to five clones were more likely to be unstable than those with two to three clones. This rare look into events in genetically complex Plasmodium infections suggests that parasite clones may be interacting in complex and unexpected ways.     

The value of comparative approaches to our understanding of puberty as illustrated by investigations in birds and reptiles

This article is part of a Special Issue "Puberty and Adolescence". Studies of birds and reptiles have provided many basic insights into the neuroendocrine control of reproductive processes. This research has elucidated mechanisms regulating both early development, including sexual differentiation, and adult neuroendocrine function and behavior. However, phenomena associated with the transition into sexual maturation (puberty) have not been a focus of investigators working on species in these taxonomic classes. Research is complicated in birds and reptiles by a variety of factors, including what can be extended times to maturation, the need to reach particular body size regardless of age, and environmental conditions that can support or inhibit endocrine responses. However, careful selection of model systems, particularly those with available genetic tools, will lead to important comparative studies that can elucidate both generalizability and diversity of mechanisms regulating the onset of reproductive maturity.     

Effects of testosterone treatment and season on the frequency of dewlap extensions during male-male interactions in the lizard Anolis sagrei

Lizards of the genus Anolis extend and retract a large and often brightly colored throat fan called a dewlap. The dewlap in most anoles is a sexually dimorphic structure. It is larger in males than females and males use the dewlap more frequently and in more contexts than do females. In the present study we investigated whether plasma testosterone (T) levels and season affect the frequency of dewlap use in male--male interactions in the brown anole, Anolis sagrei. We manipulated plasma T levels by implanting adult, castrated males with pellets that delivered no T, a moderate dose of T, or a high dose of T. In tests with stimulus males, castrated males that were treated with a moderate or with a high dose of T had a significantly higher frequency of dewlap extensions than did castrated males that received no T. However, the frequency of dewlap extensions in castrated males that received the high dose of T did not differ significantly from castrated males that received the moderate dose of T or from non-castrated control males. Males captured during the breeding season and tested in the laboratory had a significantly higher frequency of dewlap extensions than did males captured in the postbreeding season and tested in the same manner. These results suggest that plasma T levels affect how frequently males of A. sagrei extend their dewlaps in male--male interactions and that seasonal changes in male dewlap use may be due to seasonal differences in plasma T levels.     

Effects of testosterone on the development of neuromuscular systems and their target tissues involved in courtship and copulation in green anoles (Anolis carolinensis)

Male green anole lizards court females using a red throat fan (dewlap) and copulate by intromitting one of two penises (hemipenes). These structures begin sexually monomorphic, but by adulthood males have larger dewlaps, only males have hemipenes, and many of the neuromuscular components of both systems show male-biased dimorphisms. We hypothesized that testosterone (T), which increases in juvenile males but not females about a month after hatching, facilitates masculinization. To test this idea, on post-hatching day 30, gonadally intact females received either a blank or T implant, and males were either castrated or sham-castrated. At day 90, juveniles were euthanized and the length of the cartilage and cross-sectional areas of the muscle fibers and motoneurons required for dewlap extension were examined. We also measured the cross-sectional areas of the hemipenes and associated muscle fibers and motoneurons, and counted the motoneurons. T-treated females had longer cartilages and larger dewlap muscle fibers compared to those with blank implants. No effects on motoneurons were detected, and no females possessed hemipenes or associated musculature. In males, castration produced shorter dewlap cartilages and smaller hemipenes; other measures were not affected by treatment. These data indicate that components of the dewlap system differentiate relatively late in development, that T likely mediates the process, and that although components of the copulatory system are plastic in juvenile males, sexual differentiation of peripheral features is complete before day 30. The data also suggest that target structures (dewlap cartilage and hemipenes), compared to their neuromuscular effectors, are particularly sensitive to developmental T exposure.     

Factors affecting the thermal behavior of the sand lizard Liolaemus wiegmannii in natural and modified grasslands of temperate coastal dunes from Argentina

The present study describes and compares the thermal behavior of individuals of Liolaemus wiegmannii, inhabiting patches of natural grassland and modified patches with exotic trees of Acacia longifolia, by analyzing the factors affecting its behavior. Thermal behavior of L. wiegmannii was assessed by radiotracking 22 adult individuals in a coastal dune area from Argentina. In order to account for individual responses we analyzed the factors affecting thermal behavior using Generalized Linear Mixed Models. Thermal behavior of L. wiegmannii was mainly affected by the time of day and the substrate temperature. The individuals basking on bare sand in the morning shifted to filtered sunlight during midday and to the shade of clump and erect stems and herbs during the afternoon. The individuals buried in sand when the substrate temperature was low and the wind speed was high. The use of sub-shrubs and shrubs could not be explained solely by thermal factors. In natural L. wiegmannii regulated its body temperature by shuttling between microhabitats that provided them with different levels of exposure to sunlight during the day. However, in modified patches individuals varied in the choice of plants used as shaded places to mitigate high microenvironmental temperatures and they were also more exposed to full shaded sites and less to warm sand to bask, which could have negative consequences for its thermal biology.     

Performance and thermal sensitivity of the southernmost lizards in the world, Liolaemus sarmientoi and Liolaemus magellanicus

Locomotor activity performance of reptiles is largely temperature dependent and, in harsh environments with short activity periods during the day and throughout the year, plays a vital role in the fitness of the species. This particular study focuses on the performance and the thermal sensitivity for running, at different body temperatures, of the two southernmost species of lizards in the world, Liolaemus sarmientoi and Liolaemus magellanicus, studied at two locations in the south of Santa Cruz province, Argentina (51°S, 70°W and 50°S, 72°W; 133 m asl). The speed of sprint and long runs was measured in the field to determine the physiological performance of lizards at different air temperatures. In both species speed increases with the temperature, and they reach the highest performance at high temperatures. The difference between activity and thermal optima suggests that L. magellanicus has colonized its actual environment recently, and that it has not had enough time for its physiological mechanisms to evolve and achieve a maximum performance at the cold temperatures they have to tolerate at present. In contrast, L. sarmientoi achieved a high performance over a wider range of temperatures that included temperatures lower than the preferred temperatures in the lab, which they can generally find in their environment.     

Molecular evidence for a species complex in the patagonian lizard Liolaemus bibronii and phylogeography of the closely related Liolaemus gracilis (Squamata: Liolaemini)

The lizard genus Liolaemus is endemic to temperate South America and includes 190 species. Liolaemus bibronii has a large geographic distribution and inhabits a great diversity of habitats, including the Monte, Steppe, and high Andean grassland environments. Liolaemus gracilis has a similar body size and shape to L. bibronii; the two are parapatrically distributed, and L. gracilis is also widely distributed. Here we use the mtDNA cytb sequence data of these two species to investigate lizard phylogeographic patterns in southern South America. L. bibronii is paraphyletic with respect to L. gracilis, Liolaemus ramirezae, Liolaemus robertmertensi and Liolaemus saxatilis; it is composed of many genetically different allopatric haploclades, some of which are reciprocally monophyletic. We also found evidence for introgression between L. bibronii and L. gracilis in the same area that introgression was hypothesized in the Liolaemus darwinii complex. We discuss the distribution of the major haploclades with inferences of their population histories, the concordance of these clades' distributions and histories with other lizard complexes studied with the same markers and methods, and taxonomic implications of these results.     

The ascl1a and dlx genes have a regulatory role in the development of GABAergic interneurons in the zebrafish diencephalon

During development of the mouse forebrain interneurons, the Dlx genes play a key role in a gene regulatory network (GRN) that leads to the GABAergic phenotype. Here, we have examined the regulatory relationships between the ascl1a, dlx, and gad1b genes in the zebrafish forebrain. Expression of ascl1a overlaps with dlx1a in the telencephalon and diencephalon during early forebrain development. The loss of Ascl1a function results in a loss of dlx expression, and subsequent losses of dlx5a and gad1b expression in the diencephalic prethalamus and hypothalamus. Loss of Dlx1a and Dlx2a function, and, to a lesser extent, of Dlx5a and Dlx6a, impairs gad1b expression in the prethalamus and hypothalamus. We conclude that dlx1a/2a act downstream of ascl1a but upstream of dlx5a/dlx6a and gad1b to activate GABAergic specification. This pathway is conserved in the diencephalon, but has diverged between mammals and teleosts in the telencephalon.     

Coumarins and gamma-pyrone derivatives from Prangos pabularia: antibacterial activity and inhibition of cytokine release

The n-hexane and ethyl acetate extracts of the stems and the ethyl acetate extracts of roots from Prangos pabularia afforded an gamma-pyrone derivative and furanocoumarin derivatives with three glucose and gamma-pyrone (pabularin A, B and C), along with 26 previously known compounds (18 coumarins, six terpenoids and two glycosides). Their structures were established on the basis of spectroscopic studies. Of these, 16 coumarin derivatives isolated from P. pabularia were tested for antibacterial activity and inhibition of cytokine release.     

In vitro and in vivo inhibition of plant polyamine oxidase activity by polyamine analogues

Polyamine oxidase from Avena sativa L. cv. Cristal seedlings was purified to homogeneity using a simple four-step purification protocol including an infiltration washing technique. The enzyme had a high affinity for spermidine and spermine (K_m ∼ 5.5 and 1.2 μM, respectively), and also oxidized norspermidine (K_m ∼ 64.0 μM). Natural and synthetic diamines, cyclohexylamine, the putrescine analogue 1-aminooxy-3-aminopropane, and several polyamine analogues had inhibitory effects on polyamine oxidase activity and none were substrates. No inhibitory effect was observed on spermidine oxidation when the reaction product 1,3-diaminopropane was added. By contrast, 1-aminooxy-3-aminopropane showed mixed inhibition kinetics and a K_i value of 0.113 mM. In addition, in vitro enzymatic activity assays showed that the oligoamine [3,8,13,18,23,28,33,38,43,48-deca-aza-(trans-25)-pentacontene], the tetramine 1,14-bis-[ethylamino]-5,10-diazatetradecane, and the pentamine 1,19-bis-[ethylamino]-5,10,15-triazanonadecane, displayed potent competitive inhibitory activities against polyamine oxidase with K_i values of 5.8, 110.0 and 7.6 nM, respectively, where cyclohexylamine was a weak competitive inhibitor with a K_i value of 0.5 mM. These analogues did not inhibit mycelial growth of the fungus Sclerotinia sclerotiorum (Lib.) De Bary and the bacterium Pseudomonas viridiflava (Burkholder) Dowson in vitro. On the contrary, with concentrations similar to those used for polyamine analogues, guazatine (a well-known fungicide and at the same time, a polyamine oxidase inhibitor) inhibited (∼85%) S. sclerotiorum mycelial growth on Czapek-Dox medium.Finally, the analogue 1,19-bis-ethylamino-5,10,15-triazanonadecane inhibited polyamine oxidase activity observed in segments of maize leaves in vivo. The results obtained provide insights into research on the influence of polyamine oxidase activity on plant biotic and abiotic stresses.     

Application of a multi-faceted approach for the assessment of treatment response in falciparum malaria: a study from Malaysian Borneo

Thirty-two patients reporting to the Lundu District Hospital, Sarawak, Malaysian Borneo, with uncomplicated falciparum malaria were recruited into a multifaceted study to assess treatment response. Following combined chloroquine and sulphadoxine/pyrimethamine treatment the patients were followed for 28 days according to the World Health Organisation in vivo drug response protocol. The in vivo study revealed that 13 (41%) of the patients had a sensitive response to treatment, five (16%) cleared asexual stage parasites but had persistent gametocytes, 11 (34%) had RI type resistance and three (9%) had RII type resistance requiring quinine intervention before day 7 for parasite clearance. Although clinically insignificant, patients with persistent gametocytes, surviving chloroquine and sulphadoxine/pyrimethamine treatment during maturation, were placed in the reduced response to treatment group for analysis. Allelic typing detected 100% prevalence of the pfcrt K76T marker associated with chloroquine resistance and 78% prevalence of the pfdhfr NRNL haplotype associated with sulphadoxine/pyrimethamine treatment failure. High serum chloroquine levels and pfdhfr haplotypes with 相似文献   

In vivo photosystem I reduction in thermophilic and mesophilic cyanobacteria: the thermal resistance of the process is limited by factors other than the unfolding of the partners

Photosystem I reduction by plastocyanin and cytochrome c(6) in cyanobacteria has been extensively studied in vitro, but much less information is provided on this process inside the cell. Here, we report an analysis of the electron transfer from both plastocyanin and cytochrome c(6) to photosystem I in intact cells of several cyanobacterial species, including a comparative study of the temperature effect in mesophilic and thermophilic organisms. Our data show that cytochrome c(6) reduces photosystem I by following a reaction mechanism involving complex formation, whereas the copper-protein follows a simpler collisional mechanism. These results contrast with previous kinetic studies in vitro. The effect of temperature on photosystem I reduction leads us to conclude that the thermal resistance of this process is determined by factors other than the proper stability of the protein partners.