Demonstration of afferent connections of the forebrain in Emys orbicularis turtles by the peroxidase method

The transport of horseradish peroxidase (HRP) out of the injection site in the dorsal ventricular ridge was studied in turtles Emys orbicularis. Labeled cells in the forebrain were observed in the paleostriatum among fibers of the lateral forebrain bundle. In the thalamus most of cells containing the granular HRP reaction product were located in the n. rotundus, n. reuniens and perirotundal nuclei (n. dorso-medialis anterior, n. magnocellularis thalami, n (centralis) lateralis, n. dorso-medialis). Fewer labeled cells were revealed in the n. anterior and n. ventralis. The density of labeled cells in the majority of all thalamic nuclei increased if the HRP was extended from the dorsal ventricular ridge into the neostriatum and the pallial thickening with adjacent general cortex. HRP positive cells in the pretectal area, nuclei of the posterior commissura and mesencephalic ventro-lateral tegmentum were observed only in cases when the enzyme was diffused from the injection site into the neostriatum, while the HRP retrograde transport to n. geniculatus lateralis, pars dorsalis was revealed only when HRP was extended into the pallial thickening and adjacent general cortex. Ascending connections of the paleostriatum, thalamic nuclei and mesencephalic tegmentum with telencephalic structures, mainly with the dorsal ventricular ridge, were discussed.     

Thalamic neuronal reactions of the tortoise, Emys orbicularis, to visual stimuli

Reactions of 300 neurons and characteristics of their receptive fields (RF) in response to moving stimuli and diffuse illumination have been investigated in three hypothalamic regions of the tortoise Emys orbicularis. With respect to their reactions to different stimuli, the neurons investigated were divided into two groups. Neurons of the 1st type (85%) were activated by the stimuli of any size exhibiting large, small and mean RF. Adaptive changes were usually weak and mean (63%); strong changes were less frequent (37%). Some of the neurons (33) did not react to diffuse illumination, whereas other ones produced reactions of different types: 57% of the neurons exhibited a spontaneous activity, 9%--directional sensitivity. Neurons of the 2nd type (15%) reacted only to large stimuli and were characterized by large RF, strong adaptation (89%), low reactivity to diffuse illumination (46%); 35% of the neurons revealed the spontaneous activity, 20%-directional sensitivity.     

Ultrastructure of the joint receptors of the tortoise (Testudo graeca. Emys orbicularis).

The ultrastructure of the spray-like ramified encapsulated corpuscles with the primitive inner core from the joint capsules of the large limb joints of the tortoise (Testudo graeca and Emys orbicularis) was examined. Each of the branches of the receptor consists of three components. Through the middle of the receptor branche runs the nerve terminal, containing in the receptor matrix numerous mitochondria, tiny light vesicles and neurofilaments and neurotubules running in the axial way. The nerve terminal gives off on some places among the inner core cells tiny finger-like processes. The axon is surrounded by the inner core cells and their irregular plasmatic processes. Among the inner core cells and their irregular plasmatic processes there is a labyrinth of spaces, connected centrally with the periaxonal space and with the boundary space on the periphery. The inner core cells are covered on the surface, turning to the boundary space by the basal membrane. The inner core has a very primitive structure, it still lacks the typical lamellar structure. The capsule of the receptor is formed by flat cells, which surround the inner core in 1--3 layers. Between the capsule of the receptor and the inner core is the boundary space, containihg sporadical collagenous fibrils. The structure of the spray-like ramified encapsulated corpuscles with the primitive inner core from the joint capsules of the tortoise is analogous to the simple lamellar receptors from the skin of some reptiles (Von Düring 1973, 1974). The primitive structure of the inner core of the joint receptors in the tortoise reminds of the structure of the inner core of the developing simple (paciniform) corpuscles (Polá?ek and Halata 1970) and Pacinian corpuscles (Malinovsky 1974). The observed nerve endings represent a primitive, early stage in phylogeny development of the lamellar mechanoreceptors.     

Features of the dynamics of the forebrain EEG of Emys orbicularis during the solving of an extrapolation problem

Sharp EEG changes are recorded in bioelectrical activity of the dorsal cortex and dorsal ventricular edge in marsh tortoises in conditions of free movement during solving of an extrapolation task (a test of elementary reasoning ability). These changes of a pathological character, accompanied by neurotic states, were observed in some animals having correctly solved the task several times in succession (2-5), beginning with the first presentation. Such changes of EEG and behaviour were not found in tortoises that committed errors at first presentations of the task and only gradually learned correct solving. Formation of the adequate behaviour can proceed by two means: on the basis of elementary reasoning ability and learning. Disturbance of adequate behaviour in the experiment with characteristic changes of EEG testifies to a difficult state of the animal during solving of the extrapolation task.     

Electrophysiological analysis of the functional organization of cortico-cerebellar connections

The effect of stimulation of cortical association (orbito-frontal, parietal) and projection (auditory, sensomotor) areas on the activity of Purkinje neurons of the cerebellar cortex was studied in adult cats anesthetized with pentobarbital, with or without chloralose. These responses were compared with those to peripheral stimuli. Definite similarity was found between the responses of Purkinje cells to different cortical (association and projection) stimuli as regards both the types of responses of the neurons and their ability to respond. No similarity was observed in the responses of Purkinje cells to peripheral (visual, auditory, electrodermal) stimulation. Whereas almost identical numbers of neurons (over 50%) were excited in response to the different forms of cortical stimulation, the ability of the neurons to respond to peripheral stimuli differed considerably: 44.6% of neurons responded to electrodermal stimulation, 34.2% to auditory, and 18.8% to visual.Medical Institute, Kemerovo. Translated from Neirofiziologiya, Vol. 8, No. 5, pp. 483–489, September–October, 1976.     

Characterization of microsatellite loci in the European pond turtle Emys orbicularis

A set of eight highly polymorphic microsatellite markers was isolated and characterized from a genomic library enriched for dinucleotide repeats in the European pond turtle, Emys orbicularis. The markers were tested for polymorphism in a total of 33 turtles sampled in two natural ponds in the nature reserve of Kerkini, northern Greece. Number of alleles varied from 10 to 18, and expected heterozygosity ranged between 0.738 and 0.921. This novel set of loci will be particularly useful to assess fine-scale population structure and for parentage analysis in E. orbicularis.     

Absence of purinoceptors in the heart of the turtle (Emys orbicularis)

The effects of adenosine, adenosine 5'-triphosphate (ATP), a slowly degradable ATP analogue beta,gamma-methylene ATP (APPCP) and a degradation resistant ATP analogue alpha,beta-methylene ATP (APCPP) were examined on the turtle heart. Adenosine, ATP, APPCP and APCPP had no effect on the rate or force of contraction of either the atrium or ventricle. The effects of acetylcholine and noradrenaline were also examined on the turtle heart. Acetylcholine decreased the force and rate of contraction of turtle atria in a concentration-dependent manner. Noradrenaline increased the rate of contraction but caused a slight decrease in the force of contraction of the atrium. Neither acetylcholine nor noradrenaline produced an inotropic effect on the ventricle.     

H-Y Antigen Expression in Temperature Sex-Reversed Turtles (Emys orbicularis)

H-Y antigen has been used as a marker for the heterogametic sex and is assumed to be an organizing factor for the heterogametic gonad. In the turtle Emys orbicularis , H-Y antigen is restricted to the female cells, indicating a female heterogamety (ZZ/ZW) sex-determining mechanism. Moreover, the sexual differentiation of the gonads is temperature sensitive, and complete sex reversal can be obtained at will. In this framework the relationships between H-Y antigen, temperature, and gonadal phenotype were studied. Mouse H-Y antiserum was absorbed with blood and gonadal cells of control wild male and female adults, and with blood and gonadal cells from three lots of young turtles from eggs incubated at 25–26°C (100% phenotypic males), at 30–30.5°C (100% phenotypic females), or at 28.5–29°C (majority of females with some males and intersexes). The residual activity of H-Y antiserum was then estimated using an immunobacterial rosette technique. In adults, both blood cells and gonadal cells were typed as H-Y negative in males and as H-Y positive in females. In each of the three lots of young, blood cells were H-Y negative in some individuals and H-Y positive in others. The proposed interpretation is that the H-Y negative individuals were genotypic males (ZZ) and the H-Y positive were genotypic females (ZW). The gonads of these animals were then pooled in different sets according to their sexual phenotype and to the presumed genotypic sex (i.e., blood H-Y phenotype). Testicular cells were typed as H-Y negative in genotypic males as well as in the presumed sex-reversed genotypic females; likewise, ovarian cells were typed as H-Y positive in genotypic females as well as in the presumed sex-reversed genotypic males. These results provide additional evidence that H-Y antigen expression is closely associated with ovarian structure in vertebrates displaying a ZZ/ZW sex-determining mechanism.