Calotes Research Articles

Effect of Ovariectomy and Ovariectomy Followed by Estradiol-17b Treatment on the Adrenal Gland of the Garden Lizard, Calotes versicolor

Effect of Ovariectomy and Ovariectomy Followed by Estradiol-17b Treatment on the Adrenal Gland of the Garden Lizard, Calotes versicolor

Changes in Catalase Activity and Its Thermolability in Liver and Kidneys of Ageing Male Garden Lizard

Catalase activity in liver and kidneys of male garden lizards remained unchanged during maturation, but showed an increase during ageing. Instead of inactivating catalase, thermal treatment at 60 +/- 1 degree C caused a marginal increase in enzyme activity in the liver of middle-aged and kidneys of young lizards with no significant effect in old counterparts. Increase in basal enzyme activity during ageing and the maintenance of resistance against thermal inactivation of the enzyme throughout the life-span support the contention that catalase molecules in lizard tissues are not altered as a function of age, a deviation from the predictions of Orgel's error catastrophe hypothesis.

Age-related changes in glucose uptake of cerebral hemisphere slices of male garden lizards in response to starvation stress

In the male garden lizard, the glucose uptake of cerebral hemisphere slices did not change during maturation (young to middle-aged) but declined during ageing (middle-aged to old). Short-term starvation (3 days) did not cause a significant change in glucose uptake of cerebral hemisphere of young lizards but led to an increase in the parameter in both the middle-aged and old.

Age-related changes in brain and spinal cord lipids of the male garden lizard

The lipid composition (cholesterol, phospholipid triglyceride and fatty acids) of brain and spinal cord of the male garden lizard was traced during maturation and ageing. The total brain cholesterol content of both the tissues showed a significant rise during maturation, remaining almost constant thereafter. The free cholesterol content of the brain increased between middle and old age and that of the spinal cord increased during maturation. The esterified cholesterol content of the brain increased during maturation, the same parameter being not age-dependent in the spinal cord. While in the brain the phospholipid content increased during maturation followed by a decrease in old age, it showed a reverse trend in the spinal cord. The level of triglyceride in the brain declined during maturation followed by an increase in old age with no appreciable age change in the spinal cord. A comparison between young and old age-groups revealed a decrease in fatty acid content of the brain. A similar trend of decline was observed during maturation in the spinal cord. The pattern of age changes in the lipid profile of nervous tissue of the lizard, a non-mammalian vertebrate, almost conform to the pattern observed in a majority of mammals.

Circadian time dependence of erythropoietic and respiratory responses of indian garden lizard, Calotes versicolor, to mammalian urinary erythropoietin and thyroxine

The circadian stage-dependent effects of mammalian urinary erythropoietin (Ep) and thyroxine (T 4) on tissue energy metabolism ( in vivo and in vitro) and erythropoiesis were examined in the Indian garden lizard. Both T 4 and Ep increased erythropoiesis and also affected hepatic and muscle energy metabolism. Although both treatments increased circulating RBC count, irrespective of the timing of the treatment, the maximum erythropoietic stimulation was achieved only in the late photophase (9 hr after light onset, HALO). Hepatic oxygen uptake was significantly elevated at 3 and 9 HALO following in vivo Ep administration and 3, 9, and 15 HALO following in vivo T 4 injection. In contrast, in vitro addition of either Ep or T 4 to hepatic homogenates of untreated lizards significantly elevated respiratory rate, irrespective of the time of tissue collection. The rate of muscle tissue respiration was statistically elevated when Ep was administered in vivo at 9 and 15 HALO. The oxygen uptake was stimulated by T 4 only at 15 HALO. While in vitro addition of Ep to tissue homogenates significantly depressed the respiratory rate of muscle collected at 3 HALO, addition of T 4 stimulated oxygen uptake by the muscle tissue collected at 9 and 15 HALO. It is concluded that the effectiveness of Ep or T 4 largely depends upon the phase of the organism's circadian system(s).

Effect of Age on Thermal Inactivation of Glucose-6-Phosphate Dehydrogenase in Liver and Kidney of the Male Garden Lizard

A comparison between middle-aged and old lizards revealed no significant age change in glucose-6-phosphate dehydrogenase activity of liver and kidney. Thermal inactivation at 51 +/- 1 degree C induced a significantly higher degree of decline in enzyme activity of tissues of old than that of middle-aged lizards. The increase in thermolability of enzyme in liver and kidney of ageing lizards suggests an accumulation of altered enzyme molecules.

Age-Related Responses of Hepatic Glucose Uptake to Starvation and Cold Stress in Male Garden Lizards

The hepatic glucose uptake of male garden lizards did not change during maturation but showed a decline between middle-aged and old age groups. The decline in glucose uptake following starvation and cold stress was age-dependent, the young and middle-aged lizards being more responsive than the old counterparts.

Effect of thyroxine (T 4) and thiourea on the hepatic oxygen consumption of male garden lizards of three different age groups

Administration of T 4 (1 μg/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 μg T 4 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%).

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 CoCl 2 on the accelerated ageing of collagen in alloxan-diabetic lizards has been tested. Both methylene blue and CoCl 2 have been found to accelerate the ageing of collagen in normal lizards. While methylene blue enhanced the effects of alloxan in alloxanized lizards, CoCl 2 tended to reverse it. It appears that methylene blue acts as a potentiator of alloxan; CoCl 2, on the contrary, showed clear anti-ageing effects.

Effect of cold shock on age-related changes in the glucose uptake of brain slices of male garden lizard.

The glucose uptake of lizard brain slices decreased between young and middle-aged groups. There was a significant increase in the parameter between the middle-aged and old-age groups. Cold shock induced a decrease in glucose uptake of brain slices in the old, with no appreciable effect in the young and middle aged.

Body Temperature, Energy Metabolism, and Stamina in Two Neotropical Forest Lizards (Ameiva, Teiidae)

Body Temperature, Energy Metabolism, and Stamina in Two Neotropical Forest Lizards (Ameiva, Teiidae)

Influence of thyroid hormones and testosterone on the activities of hepatic mitochondrial enzymes in the Indian garden lizard, Calotes versicolor

Thyroidectomy and castration in Calotes versicolor significantly decreased the activities of hepatic mitochondrial cytochrome oxidase, α-glycerophosphate dehydrogenase (α-GPDH), and succinate dehydrogenase (SDH) when compared to sham-operated controls. Administration of thyroid hormones in thyroidectomized lizards and testosterone in castrated specimens stimulated the activities of all three enzymes studied. Chloramphenicol, when injected with thyroxine prevented the hormone-stimulated activities of cytochrome oxidase and SDH, while actinomycin D and chloramphenicol, when administered along with testosterone proprionate (low dose) prevented the testosterone-stimulated activities of cytochrome oxidase and α-GPDH.

Age-related changes in the response of hepatic succinic dehydrogenase activity to thyroxine and thiourea in lizards.

Intraperitoneal injection of thyroxine (T4; 1 microgram/g body weight on alternate days, seven doses) to male garden lizards of three different age groups caused a stimulation of hepatic succinic dehydrogenase activity, the degree of response being higher in the old (63%) than in middle-aged (39%) and young (31%). Percent inhibition of enzyme activity following thiourea treatment (0.05 mg/g body weight on alternate days, three doses) was higher in middle-aged lizards (24%) than in young (10%) and old (12%) ones.

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.

Studies on the Water-Soluble Lens Proteins of the Lizard, Calotes versicolor III. Ontogenic Changes: (lizard/crystallins/development).

Ontogeny of lens crystallins of the garden lizard, Calotes versicolor has been studied by gel filtration, polyacrylamide gel electrophoresis, 7M urea PAGE, SDS and 6M urea isoelectric focusing. Wet weight, diameter and the soluble protein content per lens were also determined as a function of age. The amount of α-crystallins increased slightly during development. The relative proportion of the putative δ-crystallins was significantly higher in the embryos than in the adult. The overall polypeptide pattern of crystallins changed markedly around the time of hatching.

Circulating thyroid hormone concentrations in relation to seasonal events in the male Indian garden lizard, Calotes versicolor

Circulating thyroxine (T 4) and triiodothyronine (T 3) were estimated by RIA in plasma samples of Calotes versicolor collected over a period of 28 months. Monthly observations on seasonal events, viz., molting, whole body O 2 consumption, abdominal fat deposition, and testes weight were also made. Plasma T 4 ranged from 0.16 to 4.63 ng/ml and T 3 from 0 to 1.76 ng/ml during the course of the year. Peaks of T 4 and T 3 could be related with prehibernating (October/November) and posthibernating (March/April) periods, when scale shedding and O 2 consumption were also enhanced. Maximum abdominal fat deposition was found in prehibernatory months (October/November). Thyroid hormone levels declined sharply with entry into hibernation. Abdominal fat deposits gradually decreased, being almost depleted by the end of hibernation. The gradual increase in thyroid hormone concentration in the later half of hibernation may be associated with increased lipolysis and preparation of the oncoming reproductive period. Although T 4 and T 3 profiles were apparently parallel, discrepancies were observed. Posthibernatory peak of T 4 was maintained much longer than that of T 3 which declined earlier. Also the rise in the prehibernatory T 3 concentration was delayed as compared to that in T 4.

Role of thyroid and testicular hormones in the oxidative metabolism of the Indian garden lizard, Calotes versicolor

l-Thyroxine ( l-T 4) and testosterone were administered separately to intact, thyroidectomized, and castrated male Indian garden lizards, Calotes versicolor (maintained under natural climatic conditions) throughout the year to study their effects on the whole-body oxygen consumption and on tissue (liver, muscle, kidney, and brain) respiration. The findings indicate that the calorigenic actions of l-T 4 and testosterone are independent of ambient temperature, and different tissues have different, temperature-independent, annual rhythms of sensitivity to l-T 4 and testosterone. Internal factors seem to play a major role in the determination of these annual tissue sensitivity rhythms. Effects of thyroidectomy and castration are brought about by decreased levels of both thyroidal and testicular hormones. It is suggested that gonadal hormones are directly involved in the oxidative metabolism of Calotes which is regulated jointly by thyroid and gonadal steroids, and the degree of involvement of the glands depends upon the energy demand and sensitivity of tissues during different months of the year.

Age-related differences in the response of hepatic oxygen consumption to thermal stress in the male garden lizard

The main aim of the present study is to compare the thermal adaptation capacity of young, middle-aged and old lizards with respect to hepatic oxygen consumption. Cold exposure (1 h at 0–4°C) caused a decline in endogenous oxygen consumption in young but did not evoke significant changes in middle-aged and old lizards. On the other hand, with 5 mM succinate the rate of respiration increased marginally only in cold-exposed old lizards. This suggests that the metabolic response to cold is age-dependent in these lizards. Exposure of homogenates at 40 ± 1°C for 15 min led to a rise in the hepatic oxygen consumption of young but not in that of either middle-aged or old lizards. There were no changes in the rate of oxygen consumption upon exposure for a similar period at 45 + 1°C of liver homogenates from lizards of three different age groups. However, exposure at 51 ± 1°C resulted in a higher degree of decline in the rate of hepatic oxygen consumption in middle-aged and old than in young lizards. Thus, the young lizards appear to be better-adapted to hyperthermic stress than the middle-aged and old.

A Golgi-type study of the hypothalamus of the lizard, Calotes versicolor

The hypothalamus of the garden lizard, Calotes versicolor, was investigated with the use of the rapid Golgi and Golgi-Cox techniques. Individual neurons belonging to different nuclear groups were identified and studied with respect to their position, orientation, nature, pattern of arborization and connections. Magnocellular neurons in the preoptic region (rapid Golgi method) are large, lobular, bipolar or multipolar elements characterized by smooth contours of their somata, and processes of differing caliber and pattern of branching. Parvocellular neurons were found to belong to the primitive and generalized isodendritic type displaying pyriform, fusiform or spindle-shaped somata. Each soma gives rise to two to four straight, sometimes curved processes, which show varying patterns of arborization. The branches extend toward the 'integrative area', comprised of medial and lateral neuropil, or among major hypothalamic tracts; they are suggested to establish extrahypothalamic contacts or to extend to adjoining nuclear zones where they may establish specific intrahypothalamic connections. CSF-contacting processes from some magnocellular and parvocellular neurons were encountered. In addition to drawing correlations between information obtained from Golgi- and Nissl preparations, an attempt has been made to understand the precise organization of neuronal elements and to study the scope and pattern of arborization in the hypothalamus of Calotes versicolor.

Temperature acclimation and phospholipid phase transition in hypothalamic membrane phospholipids of garden lizard, Calotes versicolor

Garden lizards, Calotes versicolor, were acclimated to three different temperatures, i.e., 16°C, 26°C and 36°C for a period of 30 days in ‘walk-in-environmental chambers’. The phospholipid profile and fatty acid pattern were analysed in the hypothalamus and brain of the acclimated animals. Hypothalamic and brain membrane phospholipids were prepared and their phase-transition temperatures were recorded using differential scanning calorimetry. Acclimation temperature, phospholipid composition, fatty acids of these phospholipids and the physical state and fluidity of the specific model membranes of hypothalamus (and brain) are intimately inter-related. Evidence is presented for the first time to show a possible correlation between acclimation temperature and phase-transition temperature of hypothalamic phospholipid membrane. A direct physico-chemical basis is suggested for the thermoregulatory process of hypothalamus leading to a better understanding of our knowledge on the origin of thermoregulation.