Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Lizards”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 397 records · Page 22Linked to original sources
PubMed1985

Entrainment of the circadian activity rhythm of a lizard to melatonin injections.

The circadian activity rhythms of lizards (Sceloporus occidentalis) can be entrained (synchronized) to a period of 24 hr by melatonin injections given every other day at the same time of day, but not by saline injections. The activity onsets of the entrained lizards exhibited two preferred phase-relationships (approximately 165 degrees and approximately 30 degrees) with the time of melatonin injections with the 30 degree phase only rarely observed. These results suggest that endogenous rhythms of melatonin secretion (i.e., from the pineal organ) may be involved in synchronizing circadian oscillations within the lizard's multioscillator circadian system.

Animals↗
PubMed1988

The pineal complex, aggressive behavior and thermoregulation in curly-tailed lizards, Leiocephalus carinatus.

Male Leiocephalus carinatus exhibited five types of aggressive displays, two of which were used to quantify aggression in paired encounters. After the dominant and subordinate lizard were identified, the area over parietal eye/pineal gland of the latter was shielded. This resulted in the subordinate lizard selecting higher body temperatures, exhibiting more assertive displays toward the dominant lizard, and increasing its frequency of use of a heat source that was the limited resource, as defined in the test arena. All of these responses required 4-6 days to be expressed and were reversed when the shield was removed. The results suggest that the responses are hormonally-controlled, and possibly represent an interaction between the pineal complex and discrete brain nuclei and/or the thyroid gland.

Aggression↗
PubMed1986

Effect of body temperature on the ventilatory responses in the lizard Gallotia galloti.

A new technique for recording ventilatory frequency on small lizards is described. This is based on the record of the electrical potential difference that spontaneously arises during the ventilatory cycle between an active stainless steel needle electrode, implanted on the membrane of the nasal cavity, and a reference stainless steel screw electrode implanted on the parietal bone. The nasal ventilatory signal coming from these electrodes, together with a simultaneous record of the electromyogram of intercostal muscles, was used to investigate the pulmonary ventilation of the lizard Gallotia galloti over the body temperature range 5-35 degrees C. The results suggest that the ventilation pattern of this lizard begins with a passive expiration, in which electromyographic activity is not present, followed by an active expiration and then an active inspiration, these being separated by a shorter muscular resting period. The active expiration lasts longer than the active inspiration over all the range of body temperatures studied. The ventilatory frequency increases exponentially with body temperature. The duration of the muscular activity during the ventilatory cycle, in the 10-35 degrees C range of body temperature, is approximately half the ventilatory period and decreases exponentially with body temperature at half the rate at which the ventilatory period decreases. The duration of several electromyographic events recorded during the ventilatory cycle also decreases exponentially with body temperature.

Animals↗
PubMed1991

A decrease in nasal CO2 stimulates breathing in the tegu lizard.

Tegu lizards decrease ventilatory frequency (f) when constant CO2, as low as 0.4%, is delivered to the nasal cavities. In contrast, CO2, as high as 6%, pulsed into the nasal cavities during the expiratory phase of the breathing cycle does not alter f. The purpose of the present study was to investigate further the effect of nasal CO2 pattern on f in tegu lizards. Specifically, we tested: (1) whether f was affected by CO2 delivered to the nasal cavities during the inspiratory phase of the breathing cycle, and (2) whether pulsed decreases in nasal CO2 from 4% to 2% and from 4% to 0% would remove the f inhibition caused by constant nasal CO2. Ventilation was measured using a pneumotachograph and pressure transducer in-line with an endotracheal T-tube inserted through the glottis. CO2 was delivered to the nasal cavities through small tubes inserted into the external nares. Ventilatory frequency was not significantly altered when 4% CO2 was pulsed into the nasal cavities during inspiration. Dropping the CO2 in the nasal cavities from 4% to 0% at either 15 cycles/min (0.25 Hz) or for one cycle stimulated breathing. There was no significant difference between the f response to a drop in CO2 from 4% to 0% and that to a drop in CO2 from 4% to 2%. The failure to link the phasic CO2 ventilatory response to a phase in the respiratory cycle indicates that the nasal CO2 receptors do not participate in the breath-by-breath regulation of breathing in these lizards. The observation that small decreases in nasal CO2 abolished the f inhibition caused by constant nasal CO2 provides further evidence for the ability of the nasal CO2 receptors to distinguish between pulsed and constant CO2.

Animals↗
PubMed1993

The role of surfactant in the static lung mechanics of the lizard Ctenophorus nuchalis.

We previously showed that the lung of the central Australian lizard, Ctenophorus nuchalis, contains a large amount of surfactant, the composition of which varies with body temperature. We now show that the specific compliance of the lungs of these lizards remains constant regardless of whether they were maintained at 10, 18, 27, 37 or 43 degrees C for 4 hours. In contrast, the opening pressure was constant up to 27 degrees C, but decreased at 37 and 43 degrees C. When we lavaged the lungs in situ to remove the majority of surfactant, specific compliance decreased while opening pressure increased. The lungs of C. nuchalis are essentially two bubbles, with the left one larger at low and intermediate volumes. After collapsing both lungs, the larger left lung always inflated first. However, following lavage the smaller right lung inflated first. As the larger lung, when collapsed, would have a much greater area of epithelial contact, this result is consistent with surfactant acting as an 'antiglue'. During deflation the smaller lung collapsed first, consistent with the law of Laplace. Compliance did not change in the saline-filled lung suggesting that the gas-liquid interface does not play a major role. We conclude that in the lungs of these lizards, surfactant is acting as an antiglue. This might be important during periods of apnea at low body temperatures, when residual volume is small and epithelial surfaces may come into contact.

Animals↗
PubMed1984

Comparative stereology of the lizard and frog myocardium.

The atria and ventricles of the frog and lizard were quantitated using stereologic techniques. The volume fraction (Vv) and surface density (Sv) of the free, junctional and total sarcoplasmic reticulum and mitochondria of the lizard atrium and ventricle were greater than in the corresponding chambers in the frog. Myofibrillar volume fraction and plasmalemmal surface density did not differ between the two species. The volume fraction and surface density of the free and total SR, and myocardial granules were greater in the lizard atrium than ventricle but the myofibrillar Vv and mitochondrial Vv and Sv were less. The Sv of the free SR, total SR, and the Vv and Sv of myocardial granules of the frog atrium were greater than in the frog ventricle. There were no differences between myofibrils and mitochondria in the frog atrium and ventricle.

Anatomy, Comparative↗
PubMed1991

Effects of prostaglandin F2 alpha prostaglandin E2 and arachidonic acid on the induction of oviposition in vivo and in vitro in oviparous lizards.

Gravid females of four different species of oviparous lizard were treated in vivo with varying doses of prostaglandin F2 alpha (PGF2 alpha), prostaglandin E2 or arachidonic acid (AA). In contrast to previous studies examining birds and viviparous lizards, no dosage induced oviposition in any of the treated females. All females, however, did exhibit behaviors associated with oviposition. Intact oviducts removed from gravid females and placed in organ culture did oviposit when treated with 30 or 100 ng PGF2 alpha/ml of culture media. Arachidonic acid at similar concentrations also was effective in stimulating birth. These data suggest that prostaglandins can stimulate oviposition in oviparous lizards but further suggest that their action may be inhibited by oviducal innervation until just prior to natural birth.

Animals↗
PubMed1984

Immunoglobulin classes in the garden lizard, Calotes versicolor.

Two classes of immunoglobulins have been purified from lizard serum using a combination of ion-exchange chromatography on DEAE-cellulose and gel filtration on Sephadex G-200 or on Sepharose 6B. Lizard IgM is 2-ME sensitive and has an intact molecular weight similar to human IgM. On SDS-PAGE, reduced IgM dissociates into heavy and light chains of molecular weight 70,000 and 23,500 daltons respectively. Lizards also possess a 2-ME resistant, low molecular weight immunoglobulin designated as IgY similar to avian and amphibian IgY. IgY dissociates on SDS-PAGE to yield 59,500 dalton heavy and 26,000 dalton light chains. Antisera raised in rabbits to each of the two Ig classes could be made class-specific by cross-absorption, thus indicating that IgM and IgY represent distinct isotypes.

Animals↗
PubMed1986

Effect of hydrocortisone on immune system of the lizard, Chalcides ocellatus. III. Effect on cellular and humoral immune responses.

Administration of a single injection of 1.0 mg/g body weight hydrocortisone acetate (HC) to adult lizards, Chalcides ocellatus in summer elicited a high and lasting rise in serum corticosterone and cortisol, peak levels being, however, in the physiologic ranges of 10 micrograms % (2 X 10(-7) M) and 40 micrograms % (1 X 10(-6) M), respectively. Elevation of serum corticosteroid (CS) concentrations by exogenous HC impaired the proliferative capacity of spleen cells in mixed leukocyte reaction (MLR) and significantly delayed skin allograft rejection. In vivo HC also abrogated the primary in vivo and in vitro immune responses of lizards to rat erythrocytes (RRBC). Reactivity to allogeneic cells in MLR, and antibody production against RRBC were, however, recovered when serum CS levels resumed normal, basal values i.e. at three weeks post-HC injection. These data indicate that rise in circulating CS induces severe immunosuppression in lizards.

Adrenal Cortex Hormones↗
PubMed1990

Immunological changes during pregnancy in the viviparous lizard, Chalcides ocellatus.

Splenic cells from pregnant and non-pregnant viviparous lizards (Chalcides ocellatus) were stimulated in vitro with the mitogens, concanavalin A (Con A), phytohemagglutinin (PHA) and Escherichia coli lipopolysaccharide (LPS). Cell cultures from pregnant animals were significantly less responsive to Con A and PHA than comparable cultures from non-pregnant animals. The response was depressed during the first period of pregnancy and remained low in magnitude until parturition. By contrast, the response of maternal splenic cells to LPS was reduced in pregnant lizards only during advanced pregnancy. The drastic decrease in mitogenic responsiveness was associated with marked involution of the maternal spleen. These findings strongly suggest that pregnancy impairs the immunoreactivity of viviparous lizards. Possible mechanisms for this impairment and the relationship to circulating levels of sex hormones are discussed.

Animals↗
PubMed1990

Late generated neurons in the medial cortex of adult lizards send axons that reach the Timm-reactive zones.

Double labelling autoradiography-HRP experiments were performed to examine whether late generated neurons in the medial cortex of lizards develop and send axons to their targets. One to two months after receiving a series of tritiated thymidine ([3H]T) injections to label recently generated neurons, lizards (Podarcis hispanica) were subjected to a HRP labelling experiment. HRP was stereotaxically injected into the projection areas of the medial cerebral cortex, i.e. the cortical Timm-reactive areas. Following a short survival time, lizards were sacrificed and their brains processed first for HRP histochemical detection and then for autoradiography. Many cell somata in the cell layer of the medial cortex were retrogradely labelled. A few of the HRP labelled somata also displayed autoradiographic silver granules labelling their nuclei. This indicates that their time of origin had coincided with the tritiated thymidine pulse. These doubly labelled somata are evidence that newly formed neurons grow axons that reach the areas injected with HRP.

Animals↗
PubMed1996

Adult neurogenesis in the telencephalon of a lizard: a [3H]thymidine autoradiographic and bromodeoxyuridine immunocytochemical study.

A qualitative and quantitative evaluation of adult neurogenesis in the telencephalon of a lizard was conducted using [3H]thymidine autoradiography and immunocytochemical detection of 5'-bromodeoxyuridine (BrdU). The sites of cell proliferation, the fate, and the phenotype of cells born in adulthood were determined by short and long survival experiments (7 and 30 days). Adult specimens of the Moorish gecko, Tarentola mauritanica (Sauria, Gekkonidae), received subcutaneous injections of either BrdU or [3H]thymidine. Seven days after BrdU administration most labelled cells were in the walls (ventricular zone; VZ) of the lateral ventricles, particularly close to the sulcal zones. Labelled cells in the VZ of other ventricles were practically absent. Following 30 days, labelled cells outside the VZ were seen in most telencephalic regions: olfactory bulbs (OB), medial, dorsal, and lateral cortices (MC, DC, LC), anterior dorsal ventricular ridge (ADVR), nucleus sphericus (NS), and striatum (St). Electron microscopic examination of [3H]thymidine labelled cells found in these areas revealed their neuronal identity. No labelled neurons were detected in the dorsomedial cerebral cortex (DMC), septum (Sp), or elsewhere in the telencephalon. We conclude that neurogenesis occur in most regions of the adult lizard telencephalon. The most intense neuronal production occurs in the MC. Other telencephalic regions, such as the OB, ADVR, and NS, also show a considerable rate of adult neurogenesis. We infer from our results that the new neurons are born in the walls of the lateral ventricles and then migrate to their destinations. Furthermore, we report some evidence suggesting that neurons formed in adulthood in the olfactory bulbs are generated in the distant proliferative VZ. The functional significance of neurogenesis in the telencephalon of adult lizards is unclear, but it seems to be restricted to areas that have been implicated in olfactory plasticity, learning, and memory.

Age Factors↗
PubMed1991

In vitro poly(ADPribosylation) of estrogen-induced proteins from the oviduct of the lizard Podarcis s. sicula Raf.

Poly(ADPribosylation) of nuclear proteins has been investigated in the nuclei from growing oviducts of intact and estrogen-treated spayed females of the lizard Podarcis s. sicula Raf. Isolated nuclei were incubated with [14C] NAD and nuclear proteins extracted in 0.2 m H2SO4. Labeled acid-soluble proteins were analysed by reverse-phase high-performance liquid chromatography (HPLC) and acetic acid-urea gel electrophoresis. The results reported here indicate that the ADPribosylation reaction is involved in modifying besides histone H2b, tissue specific proteins (SNPs and LMG-O). Moreover, comparable results have been obtained from nuclei prepared from the fully active oviduct of intact animals and spayed lizards stimulated with 17 beta-estradiol. It is concluded that the poly-(ADPribosylation) of hormone-induced proteins might play a role in the differentiation of the lizard oviduct.

Amino Acids↗
PubMed1986

Alloxan-induced changes in the collagen characteristics in the skin of male garden lizards, Calotes versicolor, from three age groups.

Alloxan diabetes in lizards Calotes versicolor, belonging to three age groups, induced decreased levels of percentage of solubility of collagen in dorsal and ventral skin regions after 7 days of treatment. Old lizards showed greater susceptibility to alloxan diabetes than lizards of the young and middle-age groups. There appears to be no correlation between blood-glucose level and accelerated ageing of collagen. It is suggested that, in alloxan diabetes, metabolites formed in the tissues might accelerate the ageing of collagen.

Aging↗
PubMed1989

Effect of methylene blue and cobaltous chloride on the alloxan-induced changes in collagen characteristics in the skin of garden lizard Calotes versicolor.

In the present study the effect of two chemicals such as methylene blue and CoCl2 on the accelerated ageing of collagen in alloxan-diabetic lizards has been tested. Both methylene blue and CoCl2 have been found to accelerate the ageing of collagen in normal lizards. While methylene blue enhanced the effects of alloxan in alloxanized lizards, CoCl2 tended to reverse it. It appears that methylene blue acts as a potentiator of alloxan; CoCl2, on the contrary, showed clear anti-ageing effects.

Aging↗
PubMed1989

Effect of thyroxine (T4) and thiourea on the hepatic oxygen consumption of male garden lizards of three different age groups.

Administration of T4 (1 microgram/g body-weight on alternate days) to male garden lizards of three different age groups (young, middle-aged and old) for a period of 2 weeks caused a significant rise in the hepatic oxygen consumption, the degree of response increasing with advancing age. On the other hand, when treated in vitro (5 micrograms T4 in the medium) the stimulation of hepatic oxygen consumption was observed only in lizards of the young age group. Oral administration of thiourea (0.05 mg/g body-weight on alternate days, three doses) led to a decrease in hepatic oxygen uptake, the degree of inhibition being higher in young (30%) and old (28%) than in middle-aged lizards (12%).

Aging↗
PubMedDate not supplied

Effect of cold stress and starvation on the cerebral glucose-6-phosphate dehydrogenase activity of male garden lizards of three different age groups.

In the present study we observed that the cerebral glucose-6-phosphate dehydrogenase activity of male garden lizards did not change appreciably during maturation but showed a significant rise between middle-aged and old-aged groups. Whereas cold stress (1 h at 0-4 degrees C) induced a significant increase in G6PDH activity of young animals, it caused a decrease in both middle-aged and old lizards. This decrease was more severe in the old group than in the middle-aged group. Another form of stress, 72 hours of starvation, led to a significant increase in enzyme activity in young and in middle-aged lizards with young animals showing the greater effect. The old counter-parts showed a decrease in enzyme activity after starvation stress.

Aging↗
PubMed1984

Temperature responses of standard, aerobic metabolism by the California legless lizard, Anniella pulchra.

Standard metabolic rates, measured for the lizard Anniella pulchra at 6 and 13 degrees C were statistically identical, showing notable thermal-independence at low temperature. Metabolic rates, measured at 25 and 30 degrees C, were significantly less than the rates predicted by standard equations. Thermal-independence and reduced aerobic metabolism at temperatures above the preferred range may result in water and energy savings in the fossorial habitat. Body-mass adjusted comparisons with other lizards suggest that reduced metabolism may be a correlative adaptation in small, fossorial lizards.

Animals↗