Mesotocin and vasotocin in the brain of the lizard Gekko gecko

Summary The distribution of mesotocin and vasotocin was studied in the brain of the lizard Gekko gecko with antisera specific for either peptide. Both mesotocinergic and vasotocinergic perikarya are found in the paraventricular and supraoptic nuclei of the hypothalamus, whereas vasotocinergic neurons are exclusively present in the bed nucleus of the stria terminalis and in a cell group of the rhombencephalon. The distributional pattern of the mesotocinergic fibers corresponds closely to that of the vasotocinergic fibers. However, throughout the entire brain the mesotocinergic innervation is less dense than the vasotocinergic innervation. No sex differences are present in the mesotocinergic fiber system.Abbreviations acc nucleus accumbens - bst bed nucleus of the stria terminalis - bv blood vessel - dB diagonal band of Broca - dc dorsal cortex - dth dorsolateral thalamic nucleus - lc lateral cortex - me median eminence - oc optic chiasma - ot optic tract - pag periaqueductal grey - pvn paraventricular nucleus - rc rhombencephalic cell group - sep septum - son supraoptic nucleus - tect mesencephalic tectum - vth ventrolateral thalamus     

Morphological and biochemical analyses of original and regenerated lizard tails reveal variation in protein and lipid composition

Caudal autotomy, or voluntary self-amputation of the tail, is a common and effective predator evasion mechanism used by most lizard species. The tail contributes to a multitude of biological functions such as locomotion, energetics, and social interactions, and thus there are often costs associated with autotomy. Notably, relatively little is known regarding bioenergetic costs of caudal autotomy in lizards, though key morphological differences exist between the original and regenerated tail that could alter the biochemistry and energetics. Therefore, we investigated lizard caudal biochemical content before and after regeneration in three gecko and one skink species. Specifically, we integrated biochemical and morphological analyses to quantify protein and lipid content in original and regenerated tails. All lizards lost significant body mass, mostly protein, due to autotomy and biochemical results indicated that original tails of all species contained a greater proportion of protein than lipid. Morphological analyses of two gecko species revealed interspecific differences in protein and lipid content of regenerated lizard tails. Results of this study contribute to our understanding of the biochemical consequences of a widespread predator evasion mechanism.     

Flip,flop and fly: modulated motor control and highly variable movement patterns of autotomized gecko tails

Many animals lose and regenerate appendages, and tail autotomy in lizards is an extremely well-studied example of this. Whereas the energetic, ecological and functional ramifications of tail loss for many lizards have been extensively documented, little is known about the behaviour and neuromuscular control of the autotomized tail. We used electromyography and high-speed video to quantify the motor control and movement patterns of autotomized tails of leopard geckos (Eublepharis macularius). In addition to rhythmic swinging, we show that they exhibit extremely complex movement patterns for up to 30 min following autotomy, including acrobatic flips up to 3 cm in height. Unlike the output of most central pattern generators (CPGs), muscular control of the tail is variable and can be arrhythmic. We suggest that the gecko tail is well suited for studies involving CPGs, given that this spinal preparation is naturally occurring, requires no surgery and exhibits complex modulation.     

Mitochondrial Diversity and Phylogeographic Patterns of Gekko gecko(Squamata: Gekkonidae) in Thailand

The Tokay Gecko, Gekko gecko(Linnaeus, 1758) is widely distributed in Asia and there have been concerns regarding locally decreasing populations due to overexploitation for traditional Chinese medicine. Previous studies of the genetic relationships of G. gecko populations included few populations from Thailand. Here we investigated the phylogeographic patterns of G. gecko from different regions in Thailand using mitochondrial cytochrome b sequences. Phylogenetic analyses revealed two lineages: one(Lineage A) comprising populations from Laos, Vietnam, and Thailand; and a second(Lineage B) comprising three genetically distinct groups within Thailand alone. Some Thai populations were found to have both lineages represented within them. Highly significant genetic differentiation(FST) showed geographic population structuring in Lineage B, indicating limited gene flow among groups in Thailand. Although G. gecko has a wide distribution and is well adapted to human habitation, the observed genetic structure could potentially be explained by geographic barriers such as mountain ranges. In Lineage A, our study provided primary phylogeographic evidence for lineage mixture that might be a result of human-mediated transport. Future research should include more extensive sampling across the geographic distribution of G. gecko and a landscape genetics approach could be applied for conservation planning.     

Habitat use and activity influence thermoregulation in a tropical lizard, Ameiva exsul

We examined the contributions of alterations in daily activity and behavioral selection of microhabitat to thermoregulation in a population of the lizard, Ameiva exsul (Teiidae), by combining data on lizard activity with data on the availability of sun-shade patches and operative temperatures (T_e). By comparing T_e distributions predicted by “no thermoregulation” and “only thermoregulation” hypotheses to those predicted by random use of thermal habitat, we assessed the relative contributions of microhabitat selection and daily activity to regulation of body temperature (T_b). Over the course of a day lizards maintained T_b very close to optimal temperature (T_sel) despite T_es that deviated substantially from T_sel. Data demonstrating a unimodal daily activity pattern reject the hypothesis of uniform activity throughout the day. Also, lizard activity was not positively correlated with the proportion of T_es within T_sel nor negatively correlated with the absolute deviation of available T_e from T_sel (d_e) (“only thermoregulation”). Microsite use by A. exsul deviated significantly from predictions of the “no thermoregulation” hypothesis, but our data could not reject predictions of the “only thermoregulation” hypothesis that lizards would use sun-shade patches relative to the proportion of microsites where T_e is within T_sel. Also, lizards appeared to actively select sunlit and partially shaded microsites at different times of day. Thus, despite thermal constraints imposed by the habitat, A. exsul maintained high and relatively constant T_bs throughout its daily activity period and thermoregulated effectively. This appears to be generally representative of West Indian species of Ameiva.     

Projections of the optic tectum and the mesencephalic nucleus of the trigeminal nerve in the tegu lizard (Tupinambis nigropunctatus)

Summary Fibers undergoing Wallerian degeneration following tectal lesions were demonstrated with the Nauta and Fink-Heimer methods and traced to their termination. Four of the five distinct fiber paths originating in the optic tectum appear related to vision, while one is related to the mesencephalic nucleus of the trigeminus. The latter component of the tectal efferents distributes fibers to 1) the main sensory nucleus of the trigeminus, 2) the motor nucleus of the trigeminus, 3) the nucleus of tractus solitarius, and 4) the intermediate gray of the cervical spinal cord.The principal ascending bundle projects to the nucleus rotundus, three components of the ventral geniculate nucleus and the nucleus ventromedialis anterior ipsilaterally, before it crosses in the supraoptic commissure and terminates in the contralateral nucleus rotundus, ventral geniculate nucleus and a hitherto unnamed region dorsal to the nucleus of the posterior accessory optic tract.Fibers leaving the tectum dorso-medially terminate in the posterodorsal nucleus ipsilaterally and the stratum griseum periventriculare of the contralateral tectum. The descending fiber paths terminate in medial reticular cell groups and the rostral spinal cord contralaterally and in the torus and the lateral reticular regions ipsilaterally. The ipsilateral fascicle also issues fibers to the magnocellular nucleus isthmi.     

Complete mitochondrial genome of the red-spotted tokay gecko (Gekko gecko, Reptilia: Gekkonidae): comparison of red- and black-spotted tokay geckos

Here, we sequenced the complete mitochondrial genome of the red-spotted tokay gecko (Squamata: Gekkonidae). The genome is 16,590 bp in size. Its gene arrangement pattern was identical with that of black-spotted tokay gecko. We compared the mitochondrial genome of red-spotted tokay gecko with that of the black-spotted tokay gecko. Nucleotide sequence of the two whole mitochondrial genomes was 97.99% similar, and the relatively high similarity seems to indicate that they may be separated at the subspecies level. The information of mitochondrial genome comparison of the two morphological types of tokay gecko is discussed in detail.     

Temperature-dependent rate of clutch production in a tropical lizard (Paroedura picta: Gekkonidae): Intraspecific test of the metabolic theory of ecology

Recently, a general model based on scaling of metabolic rate and reaction kinetics that predicts dependence of various biological rates on temperature and body size has been proposed as a core of the “Metabolic Theory of Ecology” (MTE). However, its thermal component has been rarely explicitly tested and its usefulness for prediction of thermal effect on key life-history traits such as reproductive rate and hence fitness is still questionable. Here, we tested its applicability to temperature-dependent rate of clutch production in a tropical gecko. The thermal effects on reproductive rates in reptiles are only poorly known and difficult to estimate, because most species lay clutches largely infrequently. Females of the Madagascar ground gecko (Paroedura picta) lay clutches in unusually short intervals, which allowed us to use this species as a model for estimation of dependence of rate of clutch production on temperature. We kept adult females at three constant temperatures (24, 27, 30 °C) and recorded their reproductive characteristics. Increasing temperature positively influences rate of clutch production, but in a manner not predicted by a simple model of reaction kinetics. The results in P. picta suggest that predictions of fitness consequences of shifts in thermal environment can be more complicated than expected under the general relationship of the MTE.     

Reactions of the rat musculoskeletal system to compressive spinal cord injury (SCI) and whole body vibration (WBV) therapy

Traumatic spinal cord injury (SCI) causes a loss of locomotor function with associated compromise of the musculo-skeletal system. Whole body vibration (WBV) is a potential therapy following SCI, but little is known about its effects on the musculo-skeletal system. Here, we examined locomotor recovery and the musculo-skeletal system after thoracic (T7-9) compression SCI in adult rats. Daily WBV was started at 1, 7, 14 and 28 days after injury (WBV1-WBV28 respectively) and continued over a 12-week post-injury period. Intact rats, rats with SCI but no WBV (sham-treated) and a group that received passive flexion and extension (PFE) of their hind limbs served as controls. Compared to sham-treated rats, neither WBV nor PFE improved motor function. Only WBV14 and PFE improved body support. In line with earlier studies we failed to detect signs of soleus muscle atrophy (weight, cross sectional diameter, total amount of fibers, mean fiber diameter) or bone loss in the femur (length, weight, bone mineral density). One possible explanation is that, despite of injury extent, the preservation of some axons in the white matter, in combination with quadripedal locomotion, may provide sufficient trophic and neuronal support for the musculoskeletal system.     

Length-tension properties of ankle muscles in chronic human spinal cord injury

Contracture, or loss of range of motion (ROM) of a joint, is a common clinical problem in individuals with spinal cord injury (SCI). In order to measure the possible contribution of changes in muscle length to the loss of ankle ROM, the active force vs. angle curves for the tibialis anterior (TA) and gastrocnemiussoleus (GS) were measured in 20 participants, 10 with SCI, and 10 gender and age matched, neurologically intact (NI) individuals. Electrical stimuli were applied to the TA and GS motor nerves at incremented angles of the entire ROM of the ankle and the resulting ankle and knee torques were measured using a multi-axis load cell. The muscle forces of the TA and GS were calculated from the torque measurements using estimates of their respective moment arms and the resulting forces were plotted against joint angle. The force–angle relation for the GS at the ankle (GSA) was significantly shifted into plantar flexion in SCI subjects, compared to NI controls (t-test, p<0.001). Similar results were obtained based upon the GS knee (GSK) force–angle measurements (p<0.05). Conversely, no significant shift in the force–angle relation was found for the TA (p=0.138). Differences in the passive ROM were consistent with the force–angle changes. The ROM in the dorsiflexion direction was significantly smaller in SCI subjects compared to NI controls (p<0.05) while the plantar flexion ROM was not significantly different (p=0.114). Based upon these results, we concluded that muscle shortening is an important component of contracture in SCI.     

A new acroeimerian (Apicomplexa: Eimeriidae) in spotted house gecko,Gekko monarchus (Schlegel) (Sauria: Gekkonidae) from Peninsular Malaysia

Systematic Parasitology - A new species of Acroeimeria Paperna &amp; Landsberg, 1989 is described from the spotted house gecko, Gekko monarchus (Schlegel) from Peninsular Malaysia. Oöcysts...     

Immunomodulatory activity of Sulforaphane, a naturally occurring isothiocyanate from broccoli (Brassica oleracea)

The effect of Sulforaphane on the immune system was studied using BALB/c mice. Intraperitoneal administration of five doses of Sulforaphane (500 microg/dose/animal/day) was found to enhance the total WBC count (12,950 cells/mm3) on 9th day. Bone marrow cellularity (23 x 10(6) cells/femur) and number of alpha-esterase positive cells (1346.66/4000 cells) were also increased by the administration of Sulforaphane. Treatment with Sulforaphane along with the antigen, sheep red blood cells (SRBC), produced an enhancement in the circulating antibody titre and the number of plaque forming cells (PFC) in the spleen. Maximum number of PFC (315.83 PFC/10(6) spleen cells) was obtained on the 6th day. Administration of Sulforaphane also showed an enhancement in the phagocytic activity of peritoneal macrophages. Moreover administration of Sulforaphane significantly reduced the elevated level of TNF-alpha production by LPS stimulated macrophages. These results indicate the immunomodulatory activity of Sulforaphane.     

Cell culture from lizard skin: a tool for the study of epidermal differentiation

An in vitro system of isolated skin cells has been developed in order to address the understanding on the factors that control the shedding cycle and differentiation of lizard epidermis. The skin from the regenerating lizard tail has been separated in epidermis and dermis, cells have been dissociated, cultivated in vitro, and studied ultrastructurally after 1–30 days of culture condition. Dissociated keratinocytes after 12 days in culture show numerous cell elongations and contain bundles of keratin or sparse keratin filaments. These cells often contain one to three 0.5–3 μm large and dense “keratinaceous bodies”, an organelle representing tonofilament disassembling. Most keratinocytes have sparse tonofilaments in the cytoplasm and form shorter bundles of keratin in the cell periphery. The dissociated dermis mainly consists of mesenchymal cells containing sparse bundles of intermediate filaments. These cells proliferate and form multi-stratified layers and a dermal pellicle in about 2–3 weeks in vitro in our basic medium. Conversely, cultures of keratinocytes do not expand but eventually reduce to few viable cells within 2–3 weeks of in vitro condition. It is suggested that dermal cells sustain themselves through the production of growth factors but that epidermal cells requires specific growth factors still to be identified before setting-up an in vitro system that allows analyzing the control of the shedding cycle in lizards.     

The role of prostaglandins and the hypothalamus in thermoregulation in the lizard, Phrynocephalus przewalskii (Agamidae)

Typically, small lizards rely heavily on behavioral thermoregulation rather than physiological mechanisms to control their rates of warming and cooling. We tested the hypothesis that prostaglandins participate in mediating the cardiovascular response to heating and cooling and temperature regulating neurons in the hypothalamus of the small lizard Phrynocephalus przewalskii. In vivo and in vitro treatments, heart rates (HRs) were all found to be higher during heating than during cooling, hysteresis was distinct below 30 and 26°C, respectively. In vivo, as administration of COX inhibitor, there were no differences in HR between heating and cooling at any body temperature and administration of agonist prostaglandins only produced a significant effect on HR below 25°C. Single-unit activity was recorded extracellularly in vitro with microelectrodes, found the firing rate of the continuous unit increased 23% when the temperature of the artificial cerebrospinal fluid dropped from 30–20°C. We conclude that prostaglandins appear to play only a limited role in modulating heart activity in Phrynocephalus przewalskii and suggest that cold-sensitive neurons in the preoptic and anterior hypothalamus (PO/AH) are involved in thermoregulatory control during heating or cooling.     

Morphology of regenerated spinal cord in Sternarchus albifrons

Summary The tail of the gymnotid Sternarchus albifrons, including the spinal cord, regenerates following amputation. Regenerated spinal cord shows a rostro-caudal gradient of differentiation. Cross sections of the most distal regenerated cord show radially enlarged ependymal cells, relatively undifferentiated cells, and numerous blood vessels. More anterior sections contain well differentiated electromotor neurons, glial cells, and myelinated axons. The number of electromotor-neuron cell bodies in cross sections of regenerated spinal cord is three to six times the number in nonregenerated cord. Distinct tracts of axons, easily identifiable in normal cord, are not distinguishable in cross sections of regenerated cord. Some reorganization of the spinal cord also appears to take place anterior to the site of transection.Individual electromotor neurons in the regenerated spinal cord have morphologies largely similar to those of normal electrocytes, i.e., cell bodies are rounded, lack dendrites, have synapses characterized by gap junctions with presynaptic axons, and lack an unmyelinated initial segment. The presence of electromotor neurons with normal morphology in regenerated spinal cord correlates with the re-establishment of relatively normal electrocyte axonSchwann cell relationships in the regenerating electric organ of this sternarchid.Supported in part by the Medical Research Service, Veterans Administration and by a grant from the National Institutes of Health. We also thank the Paralyzed Veterans of America for their support. We thank Mary E. Smith and Susan Cameron for excellent technical support     

Acetylcholinesterase inhibitory activity of a naturally occurring peptide isolated from Boana pulchella (Anura: Hylidae) and its analogs

Amino Acids - Alzheimer’s disease (AD), the most common form of dementia, is a growing problem worldwide, with 10 million incident cases registered every year. The complex etiology of AD has...     

Gas exchange morphometry of the lungs of the tokay,Gekko gecko L. (Reptilia: Squamata: Gekkonidae)

The tokay lizard (Gekko gecko) possesses singlechambered lungs, eacch of which is a mirror image of the other reflected in the midsagittal body plane. When standard techniques are employed for instilling 2% phosphate-buffered glutaraldehyde to three-quarters of the total lung capacity, neither the left nor the right lung is consistently larger. Internally, the lungs are characterized by a row of 11 dorsomedial niches and by honeycomb-like (faveolar) gas exchange tissue, which is deeper cranially than caudally. Based upon mean values for all experimental animals, a 100-g tokay would have an overall anatomical diffusion factor (respiratory surface area divided by the appropriate _ht) of 203 cm²·m^-1·100 g^-1, 61% of which is located on the interfaveolar septa. Of the total septal anatomical diffusion factor, 94% is evenly divided between the anterior and middle thirds of the lung, with 6% in the posterior third. The 39% of the anatomical diffusion factor located on the inner lung wall is predominantly (76%) in the middle and posterior lung thirds, with only 24% in the anterior region. These tendencies toward heterogeneous distribution of anatomical diffusion factor were most pronounced in a 55 g juvenile animal. In this animal the total anatomical diffusion faxtor/body mass was 3.6 times that of a 197 g adult. This difference was attributable to a greater body massspecific lung volume and respiratory surface area as well as to a greater surface-to-volume ratio in the parenchyma and to a thinner air-blood diffusion barrier in the juvenile animal.Abbreviations ADF anatomical diffusion factor - %AR percentage of potential respiratory surface area which makes up S_AR - DtO₂ diffusing capacity for air-blood tissue barrier - IUR isotropic uniform randomly distributed - bm body mass - %P percentage of lung volume devoted to parenchyma - S _A potential respiratory surface area (S _L minus the surface area of the trabeculae) - S _ANR non-respiratory surface area - S _AR respiratory surface area - S _L total internal surface area of the lung - S _v surface area-to-volume ratio in parenchyma - _ht harmonic mean thickness of the air-blood tissue barrier - V _L morphometrically determined volume of both lungs, fixed at 0.75· V _Lm - V _Lm maximal lung volume, similar to total lung capacity in mammals - V _Lr resting lung volume, similar to functional residual capacity in mammals - VP morphometrically determined volume of parenchyma of both lungs, fixed at three-quarters of V_Lm     

Merkel cells and nerve endings in the labial epidermis of a lizard

Summary Examination of the labial epidermis of the lizard Lacerta sicula revealed cells displaying all features of Merkel cells. These cells are located in the stratum basale of epidermal pegs and are arranged in clusters.