Sexual segment of the kidney of the Indian house lizard, Hemidactylus flaviviridis Rüppell

The morphology, seasonal variation and histochemistry of the sexual segment of the Indian house lizard, Hemidactylus flaviviridis are described. The sexual segment is the hypertrophied portion of the secondary and the tertiary collecting ducts of the kidney in males. The cells of the sexual segment are columnar and are loaded with secretory granules which are predominantly localized in the apical portion. These granules are either free or occasionally clumped to form an “aggregate” towards the basement membrane and are released into the lumen by apocrine secretion. Development of the sexual segment is synchronous with the spermatogenic activity of the testis and maximum development occurs in March and April when the lizards copulate. The sexual segment is secretory from the beginning of October to the end of May and is regressed during sexual quiescence (June and July). It is not developed in females and young of both sexes in any season of the year. Histochemically, the sexual segment granules are saliva resistant and PAS positive, sudanophilic and are positive to the tests for phospholipid, choline and acid phosphatase. An intense esterase activity was localized in the mucosa of the oviduct and cloaca of the female. Sperms are mixed with sexual segment secretions and are transferred to the female during copulation. A possible role for the lipid-rich sexual segment secretion as a source of energy for sperms in the female reproductive tract is discussed.     

Effects of mammalian pituitary gonadotropins on the seasonally quiescent ovary of the Indian wall lizard, Hemidactylus flaviviridis

Adult Indian wall lizards, Hemidactylus flaviviridis (Rüppell) with seasonally quiescent ovaries were treated either with ovine FSH or LH. Quantitative as well as histochemical observations revealed that only FSH could stimulate the ovarian growth and steroidogenesis whereas LH had no effect either on ovarian growth or on ovarian steroidogenesis.     

Thymic structural changes in relation to seasonal cycle and testosterone administration in wall lizard Hemidactylus flaviviridis (Ruppell)

Light microscopic and ultrastructural studies of thymus in wall lizard showed remarkable season dependent structural changes. In winter, the thymus was involuted and its cortico-medullary differentiation was not distinct. Thymocytes were sparsely distributed. The epithelial cells exhibited atrophic features such as an appreciable decrease in the nuclear-cytoplasmic ratio and accordingly reduction in cell organelles. The reconstruction of thymus commenced during spring and it became fully developed with marked delineation of cortico-medullary regions during summer. The thymus was then densely populated with thymocytes and epithelial cells showed voluminous cytoplasm having numerous cell organelles. The thymus regression started again by the beginning of autumn. The results suggest that the thymic development in wall lizard have inverse relationship with the androgen level, as the testicular steroidogenic activity was seen maximum during winter and least in summer. This assumption gets support by castration and testosterone replacement experiments. Castration of lizards during winter resulted in profound development of thymus with an appreciable increase in thymocytes mainly in the cortex region . The cortex became delineated from the medulla. Following testosterone treatment, the thymus underwent regression and was comparable to testis-intact lizard's thymus during winter season. After withdrawal of testosterone treatment, the thymus exhibited dense lymphoid and thymocyte population with a demarcation of cortico-medullary regions and sub-cortical region was regenerated.     

Ultrastructural changes in skeletal muscle of the tail of the lizard Hemidactylus mabouia immediately following autotomy

Araújo, T.H., Faria, F.P., Katchburian, E. and Freymüller, E. (2009). Ultrastructural changes in skeletal muscle of the tail of the lizard Hemidactylus mabouia immediately following autotomy. —Acta Zoologica (Stockholm) 91 : 440–446. Although autotomy and subsequent regeneration of lizard tails has been extensively studied, there is little information available on ultrastructural changes that occur to the muscle fibers at the site of severance. Thus, in the present study, we examine the ultrastructure of the musculature of the remaining tail stump of the lizard Hemidactylus mabouia immediately after autotomy. Our results show that exposed portions of the skeletal muscle fibers of the stump that are unprotected by connective tissue bulge to produce large mushroom‐like protrusions. These exposed portions show abnormal structure but suffer no leakage of cytoplasmic contents. Many small and large vesicular structures appeared between myofibrils in the interface at this disarranged region (distal) and the other portion of the fibers that remain unchanged (proximal). These vesicles coalesce, creating a gap that leads to the release of the mushroom‐like protrusion. So, our results showed that after the macroscopic act of autotomy the muscular fibers release part of the sarcoplasm as if a second and microscopic set of autotomic events takes place immediately following the macroscopic act of autotomy. Presumably these changes pave the way for the formation of a blastema and the beginning of regeneration.     

The torus semicircularis in a gekkonid lizard

The cytoarchitecture and neuromorphology of the torus semicircularis in the tokay gecko, Gekko gecko, were examined in Nissl-stained, fiber-stained, and Golgi-impregnated tissues. From a superficial position, the torus semicircularis extends rostrally under the caudal half of the optic tectum. Caudally, the two tori abut upon one another; rostrally, they diverge. The torus semicircularis consists of central, laminar, and superficial nuclei. The central nucleus consists of fusiform, spherical and triangular neurons. Their dendrites are highly branched, with numerous dendritic spines, and are oriented mediolaterally, dorsoventrally, and rostrocaudally. Fusiform and spherical neurons display two dendritic patterns: “single axis,” ramifying in one axis, and “dual axis,” exhibiting higher-order branches perpendicular to the primary dendrites. Triangular neurons exhibit a “radiate” dendritic pattern. In the rostral half of the torus semicircularis, the laminar nucleus caps the central nucleus. The laminar nucleus encircles the central nucleus in the caudal torus semicircularis. The neurons of the laminar nucleus have dendritic arrays oriented parallel to the border of the central nucleus. These dendrites exhibit a paucity of dendritic spines and higher-order branches. Fusiform and spherical neurons exhibit “single axis” and “dual axis” dendritic patterns. Triangular neurons display “radiate” patterns. The caudal superficial nucleus lies dorsal and dorsolateral to the central nucleus. The superficial nucleus is sparsely populated by small fusiform and spherical neurons with moderately branched dendrites and moderate numbers of dendritic spines. These neurons display “single axis” (fusiform neurons) as well as “dual axis” and “radiate” (spherical neurons) dendritic patterns. They are oriented either parallel to or perpendicular to the boundary of the laminar nucleus.     

In vitro effect of temperature on phagocytic and cytotoxic activities of splenic phagocytes of the wall lizard, Hemidactylus flaviviridis.

The in vitro effect of temperature on phagocytosis, nitric oxide production and interleukin-1 (IL-1) secretion by splenic phagocytes isolated from the wall lizard (Hemidactylus flaviviridis) demonstrated that changes in temperature altered non-specific defenses. The LPS-induced percentage phagocytosis and phagocytic index were recorded maximum at 25 degrees C. The phagocytic activity declined considerably when the phagocytes were incubated at low (7 and 15 degrees C) or high (37 degrees C) temperatures. The presence of bacterial lipopolysaccharide (LPS) in the incubation medium could considerably enhance the phagocytic activity of splenic phagocytes. A similar temperature-related effect was also observed on LPS-induced cytotoxic activity of phagocytes. LPS could stimulate the nitrite release indicating nitric oxide production only at 25 degrees C. Likewise, the proliferative responses of immature rat's thymocytes to LPS-induced phagocyte-conditioned medium suggest that IL-1 secretion was enhanced when phagocytes were cultured at 25 degrees C. This suggests that 25 degrees C is the optimal temperature for phagocyte functions in H. flaviviridis. The decrease or increase in temperature other than at 25 degrees C dramatically suppressed the phagocyte activities.     

Histochemical observation of the cortical zone of oocyte of Indian wall lizard, Hemidactylus flaviviridis (Rüppel).

The cortical zone of oocytes, which lies just below the follicular epithelium appears in the early stages of development, but reaches its fullest growth in vitellogenic oocytes. In the present studies it was found that the cortical zone of Hemidactylus flaviviridis consists of proteins, lipoproteins, carbohydrates, fatty yolk, RNA and little amount of DNA in mature oocytes along with mitochondria and Golgi bodies. In the early oocyte, this zone is fine granular in nature, but during the yolky stages of oocyte, it becomes filled by the vacuolar structure, which shows in it's the presence of fatty and compound yolk. The L1 and L2 types of lipid globules are also observed in the cortical zone during vitellogenic oocyte.     

Dose and time-related in vitro effects of glucocorticoid on phagocytosis and nitrite release by splenic macrophages of wall lizard Hemidactylus flaviviridis

Glucocorticoids (GC) are usually considered to be immunosuppressive and anti-inflammatory. However, recent studies in mammals have demonstrated the diverse effects of GC on non-specific host-defense mechanism, depending on dose or duration of treatment. Hence, in the present study in vitro dose and time-related effects of glucocorticoid, i.e. hydrocortisone (HC) on phagocytosis and nitrite production by LPS-induced splenic macrophages in wall lizard Hemidactylus flaviviridis has been investigated. Hydrocortisone suppressed percentage phagocytosis, phagocytic index and nitrite production by splenic macrophages even at the lowest concentration (10(-13) M) for a short-term exposure (4 h). Hydrocortisone-induced suppression enhanced with the increase of concentration or duration of exposure time. The suppressive effect of hydrocortisone on phagocytic and cytotoxic activities of splenic macrophages was further corroborated since the pre-exposure of macrophages to glucocorticoid-receptor blocker (RU 486) considerably reduced the hydrocortisone-induced suppression of phagocytosis and nitrite production. The present study suggests that GC instead of diverse effects, has dose- and time-dependent immunosuppressive effect on non-specific host-defense immune responses in wall lizard H. flaviviridis.