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At least 1,063 records · Page 59Linked to original sources
PubMed1996

Larval development of tectal efferents and afferents in Xenopus laevis (Amphibia Anura).

The development of tectal connections in Xenopus laevis had been investigated using the degeneration technique to demonstrate the efferent pathways and the retrograde HRP transport to label the afferent pathways. Bilateral tectal efferents were present as soon as the beginning of metamorphosis. Ascending efferents originated from the anterior tectal part terminate in the secondary visual thalamic centres whereas the descending efferents coming from the posterior tectal part reached the tegmentum and the medulla oblongata. At this same time, the optic tectum already received secondary visual afferents originating in the ipsilateral pretectum and non-visual afferents from the ipsilateral semicircular torus and tegmentum. Some sparse bilateral isthmotectal connections were also present. Later, efferent pathways showed an increasing number of fibres whereas the sites of origin of afferents became more diversified: the dorsal thalamus, the suprachiasmatic area, the tegmental nuclei and in the medulla oblongata, the reticular and octavolateral areas sent bilateral projections to the optic tectum. At the end of metamorphosis, we noted ipsilateral olivotectal fibres and reciprocal connections between the tectum and the area of the Vth nerve. These last findings and the presence of the following direct projections, not previously reported in Anurans: the reciprocal connections between the tectum and the semicircular torus or the octavolateral area, underline the implication of the optic tectum in the multisensory (visual, acoustic, vibratory) integration elicited during the larval behavior. Also, the relations between the optic tectum and the lateral line system are particularly examined in the discussion.

Afferent Pathways↗
PubMed1997

[Gene diffusion in hybrid populations of green frogs Rana esculenta L., 1758 complex (Amphibia, Ranidae) from the Dnepr Basin].

Population-genetic analysis of hybrid populations of green frogs from the Dnepr basin demonstrated limited gene introgression in diploid hybrids in addition to semiclonal reproduction, which is typical for Rana esculenta hybrids. Introgression is largely confined to the Ldh-B locus: the gene of R. lessonae is introduced into the R. ridibunda genome. This phenomenon is unstable as it is geographically restricted and absent in populations of the E-L type.

Animals↗
PubMed1998

Identification and localization of neurohypophysial peptides in the brain of a caecilian amphibian, Typhlonectes natans (Amphibia: Gymnophiona).

The amphibian order Gymnophiona contains more than 150 different species of caecilians. The characterization and distribution of neurohypophysial peptides, however, has not been described for any member of this order. By using high-performance liquid chromatography, radioimmunoassay, and mass spectrometry, we identified the peptide arginine vasotocin (AVT) in brain and pituitary extracts from the caecilian Typhlonectes natans. By using immunocytochemistry, we found five populations of AVT-immunoreactive (AVT-ir) cells in the brain of T. natans. AVT-ir cell bodies were located in the preoptic area, amygdala pars medialis, ventral thalamus, dorsal hypothalamic nucleus, and nucleus of the solitary tract. AVT-ir fibers and terminal fields were widespread. We also identified a mesotocin-like peptide. The distribution of this peptide in the brain of T. natans was more restricted than the distribution of AVT. Mesotocin-like-immunoreactive cell bodies were located almost exclusively in the preoptic area, with only a few other cells located in the amygdala pars medialis. This caecilian species, therefore, possesses neurohypophysial peptides that are similar in their structure and distribution to the peptides found in anuran and urodele amphibian orders.

Amphibians↗
PubMed1998

Helminths of the Canadian toad, Bufo hemiophrys (Amphibia: Anura), from Alberta, Canada.

Forty adult Bufo hemiophrys from Alberta, Canada, were examined for helminths. Four species were found: a trematode, Gorgoderina simplex, and 3 nematodes, Cosmocercoides variabilis, Oswaldocruzia pipiens, and Rhabdias americanus. Rhabdias americanus had the highest prevalence of helminths (73%); C. variabilis had the highest mean intensity (26+/-33 SD). Bufo hemiophrys represents a new host record for each species of helminth.

Alberta↗
PubMed1978

[Contribution of divalent cations to the maintenance of membrane potentials in the oocytes of Pleurodeles waltlii Michah (Amphibia, Urodela)].

When the external concentration of Ca and Mg is changed, the oocyte membrane potential, in the Urodela Amphibian: Pleurodeles waltlii, is not significantly modified. The addition of chelator agents, EGTA and EDTA in Ca, Mg free Steinberg solution promotes a membrane depolarisation and the rise of membrane conductance. It is concluded that divalent ions Ca++ and Mg++ are needed to maintain a potential difference between internal and external medium of the oocyte.

Animals↗
PubMedDate not supplied

[The correlation of the ecological niches of the common (Rana temporaria L.) and of the moor (Rana arvalis Nilss.) frogs (Anura, Amphibia)].

During 25 years ecology and population dynamic of two brown frog species (Rana temporaria and R. arvalis) were studied in Moscow region, Solovki island and South Ural. We compared life cycles characteristics, namely biotope preferences, diet, migration, enemies, hibernation places using own and available literature data. Then we analyse how these parameters are changed among the species area and ecological niches were compared. We found that these two species do not compete in any stage of life cycle. Ecological niches are very closed and differences are determined generally by abiotic factors. So, R. temporaria prefers more wet biotope and more sensitive to acidity (low pH value). Differences in spawning time do not associate with interference in spawning places. We conclude that interspecific competition did not take place neither in the past nor in present and the reason of differences in ecological niches are determined by separate ways of evolutionary development of these species.

Animals↗
PubMed1976

[Transfer of behavior patterns through transplantation of anlagen of neuro-anatomic structures in amphibian larva. 1. Xenoplastic exchange of medulla anlagen between Xenopus laevis and Hymenochirus boettgeri (Amphibia, Anura)].

By transplantation of parts of the neural plate (latter medulla oblongata) from Xenopus laevis (Daud.) to Hymenochirus boettgeri (Torn.) larval chimaeras were obtained, which showed donorlike rhythmical movements of the mouth and pharyngeal region, movements which the host species lacks. Nevertheless, some of these tadpoles were still able to catch small prey in a reaction which is typical for the host and lacking in the donor.

Amphibians↗
PubMed1978

[Blood supply of the compact and spongy myocardium of fish, amphibia and reptiles].

Coronal arteries were injected with lead carbonate suspension and with Indian ink and cleared preparations 150--300 mkm thick were made in 195 hearts of fish, amphibians and reptiles and studied roentgenographically. It was stated that in Chondrichthyes (shark, skate) and in Chondrostei (beluga, stellate sturgeon, sturgeon), as well as in alligator both compact and spongy myocardium of the cardiac ventricle possess blood vessels. In teleostei, amphibians and reptiles (except alligator) spongy myocardium is avascular and receives its nutrition from the ventricle. In view of the data on the presence of blood vessels in the spongy myocardium in some vertebrates, it is impossible to accept the theory suggested by Grant and Regnier according to which vessels in the heart walls appear only in connection with compactization of the myocardium. Vascularization of the spongy myocardium is closely connected with oxygen saturation of the blood flowing through the heart. When this saturation is not satisfactory, the spongy myocardium has blood vessels. In alligator, vascularization of the spongy myocardium is connected with the fact that the heart has four chambers and there are arterial and venous blood streams.

Alligators and Crocodiles↗
PubMed2001

Introgressive hybridization in Rorippa (Brassicaceae): gene flow and its consequences in natural and anthropogenic habitats.

Introgressive hybridization between three Rorippa species (R. amphibia, R. palustris and R. sylvestris) in northern Germany has been studied using isozymes and noncoding chloroplast DNA (trnL/F spacer). Our results provide substantial evidence for different patterns of gene flow in natural and in anthropogenic environments. Hybridization and bi-directional introgression (chloroplast DNA and allozymes) between R. amphibia and R. sylvestris were detected at the river Elbe, which is one of the last rivers in Central Europe showing a natural dynamic of erosion and sedimentation. The natural dynamic of the Elbe leads to periodic habitat disturbance and the temporal breakdown of ecological isolation barriers between R. amphibia and R. sylvestris. However, the high dynamic does not provide the opportunity for persistence of the morphologically intermediate hybrid R. x anceps (R. amphibia x R. sylvestris). We did not find hybrid zones between R. amphibia and R. sylvestris in the more anthropogenic landscape of northwest Germany. However, contact zones between R. amphibia and R. palustris were detected in drainage ditches in northwest Germany. We found substantial evidence for unidirectional introgression of R. palustris markers (chloroplast DNA and allozymes) into R. amphibia in the man-made habitats. The R. amphibia introgressants in the drainage ditches often showed strongly serrate upper cauline leaves instead of the entire upper cauline leaves typical for R. amphibia. We argue that landscape melioration in northwest Germany, particularly the creation of drainage ditches, favoured both hybrid-zone formation and ecotypic differentiation within R. amphibia.

Brassicaceae↗
PubMedDate not supplied

[Are the injuries caused by the "water bombs" dropped by the Canadair airplane blast injuries?].

During the forest fire extinguishing in summer using the fire-fighting amphibia (the Canadair) seven soldiers were injured by the "water bomb" dropped from the amphibia and two soldiers died. The way of injury occurrence as well as type and nature of injuries, imposed the question to the author: could it be a case of blast injuries, especially of primary blast injuries? Except for pure scientific reasons, a positive answer could have a practical importance both in regulation of work of persons engaged in fire combat on the ground during extinguishing of fire by the amphibia as well as for physician's work with those exposed to water impact from the plane and who could be eventually injured. Defining any mechanical injuries as transmission of the corresponding kinetic energy, the author considers that the mechanism of injury occurrence of the internal organs caused by the impact of the "water bomb" from the amphibia is the transmission of the energy impact wave into the body. The author has concluded that the impact of the "water bomb" dropped from the fire fighting amphibia can cause changes in the internal organs which are characteristic of primary blast injury. It is proposed that persons exposed to impact even in the absence of visible changes should be subjected to otorhinolaryngologic, and, in special cases, to pulmonary examinations.

Accidents, Occupational↗