Heterothermic Vertebrates Research Articles

Relationships between seasonal (spring, summer, autumnal) thermal variations and cell proliferation in heterothermic vertebrates, as revealed by PCNA expression in the brain of adult Triturus carnifex

Inspired both by the literature reports and our previous findings on the question if a seasonal cycle alone, consisting of temperature and photoperiod variations, might impact on or activate natural proliferative fluctuations or unmask a latent spontaneous proliferative power in adult brain of poikilothermal Anamnia (fresh water, earth-dwelling) and Amniota (terrestrial), consequently allowing for encephalic reparative and even regenerative potentialities, an investigation has been carried on in normal adult brain of Triturus carnifex caught in nature in spring, summer, autumn. Cells immunostained for PCNA, i.e. cycling cells, were found scattered (“matrix cells”) in the olfactory territories, where they appeared scarce in spring, more frequent in summer, noticeable in autumn; also, immunostained cells were found clustered in “matrix areas”, also named zonae germinativae dorsales and ventrales, in the telencephalic hemispheres: few clusters in spring, an intermediate condition in summer, frequent cell groups in autumn. These results reveal an increasing trend in proliferation from spring, through summer, to autumn. This scenario was appreciable in the forebrain, mainly in the olfactory and telencephalic districts, which is the typical site of stem cells. Signs of potential proliferative activity are well appreciable in the urodele Amphibians, which are the best provided among vertebrates with reparative and regenerative power and possess the richest endowment of dormant cells susceptible to be recruited to proliferation.

Relationships between summer thermal variations and cell proliferation in heterothermic vertebrates, as revealed by PCNA expression in the brain of adult Rana bergeri (Günther, 1986)

About the issue if the natural encephalic proliferative activities can be influenced by the seasonal (thermal and photoperiodic) cyclic fluctuations in adult earth-dwelling Anamnia and poikilothermal Amniota there is a gap regarding expressly summer season alone in literature reports on autoradiographic studies in frog. The actual study suggests that the brain proliferative pattern in Rana bergeri collected in the wild in summer is intermediate between those previously observed in spring and autumn. This would seem to indicate a proliferative increase from spring to autumn. This pattern mainly appears in the forebrain, typically in the olfactory portion where the stem cells are identifiable as scattered “matrix“ cells in the ependyma and grey matter, and in the telencephalic district, where these cells are grouped as “matrix” areas in the well-known zonae germinativae dorsales and ventrales.

A HISTOLOGICAL STUDY ON HEPATIC STRUCTURE OF Lyciasalamandra arikani (URODELA: SALAMANDRIDAE)

The liver is one of the most important internal organ in the body. It plays a prominent role in many processes in the body, particularly those concerned with its metabolism (protein synthesis, storage metabolites, bile secretion and detoxification). This report represents the histological characterization of liver Lyciasalamandra arikani, endemic salamander to Turkey. Hematopoietic tissue structures were examined in the connective tissue of the perihepatic regions. The liver of L. arikani probably possesses immunologic capabilities due to the presence of lymphocytes in the perihepatic regions. The hepatic lobules consisted of both hepatocytes and sinusoidal blood capillary networks, in which hepatocyte-sinusoidal structures were formed. The hepatocytes were polygonal and had a rounded nucleus. There is a lot of differing content of melanin containing cells in the hepatic parenchyma. Periodic acid-Schiff (PAS) staining method showed large glycogen deposits in the clusters of melanin granules. These melano-macrophage centers probably act significant role in organs of heterothermic vertebrates including providing energy and protection against pathogens due to fact that heterothermic vertebrates can produce energy slowly and so are torpid related the blood flow rate at low temperatures.

Relationships between seasonal thermal variations and cell proliferation in heterothermic vertebrates, as revealed by PCNA expression in the brain of adult Podarcis sicula

In adult terrestrial heterothermic vertebrates, spontaneous or experimentally induced plasticity of the brain is widely demonstrated. This phenomenon is more pronounced in Amphibians than in lacertilians, the most investigated among the Reptiles. In the lizard it has been observed that the summer photoperiod and temperature exert a positive influence on the proliferative activity of cerebral putative stem cells, which then differentiate into glial or neuronal cells. In the present investigation, the behaviour of proliferating neural cells has been investigated by immunocytochemistry in the brain of normal adult Podarcis sicula caught in their habitat in summer. The results, qualitatively evaluated, were compared with those on normal lizards of the same species, caught from the wild in late spring and previously analysed by the same author. The comparison showed that summer environment stimulates cell proliferation, although to a limited extent. This response seems to involve the quiescent cells which mainly populate the ependymal layer of the forebrain, the telencephalic hemispheres being the best provided with these undifferentiated cells, while no substantial differences from spring values were found in more caudal cerebral portions. The comparison between present findings and previously reported ones indicates that summer environment stimulates the proliferation of putative neuronal stem cells but only in the forebrain; this proliferation might not be sufficient to support the regeneration upon partial removal of this portion of the encephalon, and previous findings of a much higher regenerative capacity in the lizard brain upon cerebral injury might depend on factors linked to injury itself or to the studied species and their habitat.

Relationships between seasonal thermal variations and cell proliferation in heterothermic vertebrates, as revealed by PCNA expression in the brain of adult Rana burger (Günther, 1986)

The cyclic variations of temperature with seasons, which are accompanied by variations in photoperiod, can activate proliferation in stem cells which survive in various organs and tissues of adult vertebrates, both poikilo- (aquatic and terrestrial) and homeothermic (male songbirds and Mammals). In the brain of these organisms such stem cells are mainly placed in the ependymal and/or sub-ependymal layers. To assess the influence of environmental temperature on the proliferative activity of those cells, an immunocytochemical investigation has been carried out on the brain of normal adult Rana bergeri, taken from the wild in late autumn and immediately submitted to observation. The results were compared with those of previous investigations on the same animal species, caught in their habitat in late autumn as in this study, but housed in standard laboratory environment for several days before beginning the experiments. I have now observed a widespread reduction in proliferation. This finding discordance is reasonably imputable to the former stay of the specimens in a thermostable environment during the previous investigations and appears in agreement with what is known from the literature for comparable experimental conditions, suggesting that a stay for days in a thermally stable, warm environment can counteract the anti-proliferative effect of exposition to the late autumn climate.

New Viruses fromLacerta monticola(Serra da Estrela, Portugal): Further Evidence for a New Group of Nucleo-Cytoplasmic Large Deoxyriboviruses

Lizard erythrocytic viruses (LEVs) have previously been described in Lacerta monticola from Serra da Estrela, Portugal. Like other known erythrocytic viruses of heterothermic vertebrates, these viruses have never been adapted to cell cultures and remain uncharacterized at the molecular level. In this study, we made attempts to adapt the virus to cell cultures that resulted instead in the isolation of a previously undetected Ranavirus closely related to FV3. The Ranavirus was subsequently detected by polymerase chain reaction (PCR) in the blood of infected lizards using primers for a conserved portion of the Ranavirus major capsid protein gene. Electron microscopic study of the new Ranavirus disclosed, among other features, the presence of intranuclear viruses that may be related to an unrecognized intranuclear morphogenetic process. Attempts to detect by PCR a portion of the DNA polymerase gene of the LEV in infected lizard blood were successful. The recovered sequence had 65.2/69.4% nt/aa% homology with a previously detected sequence from a snake erythrocytic virus from Florida, which is ultrastructurally different from the studied LEV. These results further support the hypothesis that erythrocytic viruses are related to one another and may represent a new group of nucleo-cytoplasmic large deoxyriboviruses.

Temperature dependence of haemoglobin–oxygen affinity in heterothermic vertebrates: mechanisms and biological significance

As demonstrated by August Krogh etal. a century ago, the oxygen-binding reaction of vertebrate haemoglobin is cooperative (described by sigmoid O(2) equilibrium curves) and modulated by CO(2) and protons (lowered pH) that - in conjunction with later discovered allosteric effectors (chloride, lactate and organic phosphate anions) - enhance O(2) unloading from blood in relatively acidic and oxygen-poor tissues. Based on the exothermic nature of the oxygenation of the haem groups, haemoglobin-O(2) affinity also decreases with rising temperature. This thermal sensitivity favours oxygen unloading in warm working muscles, but may become detrimental in regionally heterothermic animals, for example in cold-tolerant birds and mammals and warm-bodied fish, where it may perturb the balance between O(2) unloading and O(2) requirement in organs with substantially different temperatures than at the respiratory organs and thus commonly is reduced or obliterated. Given that the oxygenation of haemoglobin is linked with the endothermic release of allosteric effectors, increased effector interaction is an effective strategy that is widely exploited to achieve adaptive reductions in the temperature dependence of blood-O(2) affinity. The molecular mechanisms implicated in heterothermic vertebrates from different taxonomic groups reveal remarkable variability, both as regards the effectors implicated (protons in tunas, organic phosphates in sharks and billfish, chloride ions in ruminants and chloride and phosphate anions in the extinct woolly mammoth, etc.) and binding sites for the same effectors, indicating multiple evolutionary origins, but convergent physiological functionality (reductions in temperature dependence of O(2) -binding affinity that safeguard tissue O(2) supply).

Temperature affects insulin-like growth factor I and growth of juvenile southern flounder, Paralichthys lethostigma

Temperature profoundly influences growth of heterothermic vertebrates. However, few studies have investigated the effects of temperature on growth and insulin-like growth factor I (IGF-I) in fishes. The aim of this study was to examine effects of temperature on growth and establish whether IGF-I may mediate growth at different temperatures in southern flounder, Paralichthys lethostigma. In two experiments, juvenile flounder were reared at 23 and 28 degrees C and growth was monitored for either 117 or 197 days. Growth was similar across treatments in both experiments until fish reached approximately 100 mm total length. Body size then diverged with fish at 23 degrees C ultimately growing 65-83% larger than those at 28 degrees C. Muscle IGF-I mRNA, plasma IGF-I, and hepatosomatic index (HSI) were significantly higher in flounder at 23 degrees C, whereas hepatic IGF-I mRNA abundance did not differ with treatment. Muscle IGF-I mRNA was correlated with HSI, while plasma IGF-I was correlated with body size, hepatic IGF-I mRNA, and HSI. These results demonstrate a strong effect of temperature on flounder growth and show that temperature-induced variation in growth is associated with differences in systemic IGF-I and local (i.e., muscle) IGF-I mRNA levels. The results also support the use of plasma IGF-I and HSI as indicators of flounder growth status.

Pontine influences on respiratory control in ectothermic and heterothermic vertebrates

Respiratory rhythm generators appear both evolutionarily and developmentally as paired segmental rhythm generators in the reticular formation, associated with the motor nuclei of cranial nerves V, VII, IX, X, and XII. Those associated with the Vth and VIIth motor nuclei are "pontine" in origin and in fishes that employ a buccal suction/force pump for breathing the primary pair of respiratory rhythm generators are associated with the trigeminal nuclei. In amphibians, while the basic respiratory pump remains the same, the dominant site of respiratory rhythm generation has been assumed by the facial, glossopharyngeal and vagal motor nuclei. In reptiles, birds and mammals, in general there is a switch to an aspiration pump driven by thoraco-lumbar muscles innervated by spinal nerves. In these groups, the critical sites necessary for respiratory rhythmogenesis now sit near the ponto-medullary border, in the parafacial region (which may underlie expiratory-dominated, intercostal-abdominal breathing in non-mammalian tetrapods) and in a more caudal region, the preBotzinger complex (which may underlie inspiratory-dominated diaphragmatic breathing in mammals).

Cellule PCNA positive nel cervelletto di un Teleosteo adulto,Carassius carassius L.

Among heterothermic Vertebrates, only Teleosts have a cerebellum with elements that conserve embryonic characters into adulthood; such cells are present in other encephalic regions but are more abundant in the cerebellum. This is due to the presence in Teleosts of generalized tissue proliferation that does not cease when the organism reaches full body size, a phenomenon reflected in proliferation and/or maturation events that influence the plasticity of the nervous tissue and thus the brain. Kirsche (1967) reported the persistence in the adult Teleost cerebellum of cells with characteristics similar to those of neuroblasts. In subsequent decades, the expression of spontaneous proliferation was studied in juvenile and/or adult Teleosts, first with histological methods (especially autoradiography after inoculation with3H-thymidine) and then with immunocytochemical methods. Recently, we employed a current immunocytochemical test based on Proliferating Cell Nuclear Antigen (PCNA), a reliable marker for thein situ detection of cells in the S phase, to investigate normal proliferation first in the telencephalon and then in the mesencephalon in adults ofCarassius carassius. In the present study, the immunocytochemical expression of PCNA, indicating spontaneous mitotic activity, was detected in different degrees in the main cerebellar components (valvula cerebelli, corpus cerebelli, eminentiae granulares). Cells showing DNA synthesis were distributed in both the molecular and granular layers. As found previously for the telencephalon and mesencephalon, our results are virtually identical to those reported in the literature; the smaller amount of PCNA immunoreactivity can perhaps be attributed to the age of our specimens.

Resistance to disuse atrophy in a turtle hindlimb muscle

The purpose of this study was to characterize the changes in a turtle hindlimb muscle (external gastrocnemius) after exposure to three conditions of disuse: immobilization, tenotomy, and spinalization. Histochemical analysis and measurement of muscle fiber cross-sectional area and weighted cross-sectional area were used to assess the potential conversion of muscle fiber types and changes in fiber size. It was found that unlike its counterpart in mammalian endotherms, the external gastrocnemius muscle of the adult turtle, Trachemys scripta elegans, was remarkably resistant to each model of reduced muscle function. It is suggested that such resistance to disuse is due to intrinsic mechanisms that enable heterothermic mammals and ectothermic vertebrates to tolerate an unfavorable climate and food and water shortages by using hypometabolic states.

Melano-macrophage centres and their role in fish pathology.

Melano-macrophage centres, also known as macrophage aggregates, are distinctive groupings of pigment-containing cells within the tissues of heterothermic vertebrates. In fish they are normally located in the stroma of the haemopoietic tissue of the spleen and the kidney, although in amphibians and reptiles, and some fish, they are also found in the liver. They may also develop in association with chronic inflammatory lesions elsewhere in the body and during ovarian atresia. In higher teleosts, they often exist as complex discrete centres, containing lymphocytes and macrophages, and may be primitive analogues of the germinal centres of lymph nodes. Melano-macrophage centres usually contain a variety of pigments, including melanins, and these increase in range and volume in older fish or in the presence of cachectic disease. Melano-macrophage centres act as focal depositories for resistant intracellular bacteria, from which chronic infections may develop. Iron capture and storage in haemolytic diseases appears to be a primary function, but antigen trapping and presentation to lymphocytes, sequestration of products of cellular degradation and potentially toxic tissue materials, such as melanins, free radicals and catabolic breakdown products are among other functions that have been ascribed. Recent work suggests that they are a site of primary melanogenesis rather than mere storage. Melano-macrophage centres increase in size or frequency in conditions of environmental stress and have been suggested as reliable biomarkers for water quality in terms of both deoxygenation and iatragenic chemical pollution.

Warm-Up Rates and Body Temperatures in Bees: The Importance of Body Size, Thermal Regime and Phylogeny

ABSTRACT We assess the importance of body mass and the minimum ambient temperature at which foraging occurs in determining the warm-up rates and thoracic temperatures in flight at an air temperature of 22 °C of 55 species of bee (Hymenoptera: Apoidea) from six families adapted to a variety of thermal environments. To control for the effects of taxonomic differences in the relationships between these variables, we use multiple regression incorporated in the phylogenetic regression method developed by Grafen (1989). The prediction made by May (1976) that for very small heterotherms warmup rate will correlate positively with body mass is confirmed when the effects of phylogeny and the thermal environment to which the bee is adapted have been controlled for. The relationship between warm-up rate and body mass within the Apoidea is thus not an extension to lower body masses of the relationship found for heterothermic vertebrates. Having controlled for the effects of body mass in our analyses, we demonstrate that bees able to fly at lower ambient temperatures have higher thoracic temperatures and warm-up rates than bees adapted to warmer environments. There is some suggestion that kleptoparasitic bees, being freed from the need to forage in order to provision cells, have lower warm-up rates than provisioning species. The significance of these relationships in the ecology of bees is discussed in relation to studies of body temperatures and warm-up rates in bees and other insects.