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PubMed1989

Detection of adrenocorticotropin-related and alpha-melanocyte-stimulating hormone-related substances in the anterior pituitary of larval and adult Ambystoma tigrinum (class: Amphibia).

Immunohistochemical analysis revealed the colocalization of ACTH-related immunoreactive forms and alpha-MSH-related immunoreactive forms in corticotropic cells of the anterior pituitary of larval Ambystoma tigrinum. Subsequent analysis of acid extracts of anterior pituitaries obtained from larval, neotene, and postmetamorphic adults indicated that the molar ratio of ACTH(1-39) to alpha-MSH was, respectively, 2.5:1, 1:1.5, and 1:1.3. However, in sexually mature adults the molar ratio of ACTH(1-39) to alpha-MSH was 8:1. These results indicate that before and immediately after metamorphosis, both ACTH(1-39) and alpha-MSH are major end products of corticotropic cells in this species. As postmetamorphic animals reach sexual maturity, ACTH(1-39) is a major end product of corticotropic cells and only trace amounts of alpha-MSH are produced. Thus in A. tigrinum the proteolytic processing of ACTH in corticotropic cells is developmentally regulated. The alpha-MSH-related peptide produced by the corticotropic cells appears to be an ACTH(1-13)amide-like form.

Adrenocorticotropic Hormone↗
PubMed2006

Water balance of field-excavated aestivating Australian desert frogs, the cocoon-forming Neobatrachus aquilonius and the non-cocooning Notaden nichollsi (Amphibia: Myobatrachidae).

Burrowed aestivating frogs of the cocoon-forming species Neobatrachus aquilonius and the non-cocooning species Notaden nichollsi were excavated in the Gibson Desert of central Australia. Their hydration state (osmotic pressure of the plasma and urine) was compared to the moisture content and water potential of the surrounding soil. The non-cocooning N. nichollsi was consistently found in sand dunes. While this sand had favourable water potential properties for buried frogs, the considerable spatial and temporal variation in sand moisture meant that frogs were not always in positive water balance with respect to the surrounding soil. The cocoon-forming N. aquilonius was excavated from two distinct habitat types, a claypan in which frogs had a well-formed cocoon and a dune swale where frogs did not have a cocoon. Cocoons of excavated frogs ranged in thickness from 19.4 microm to 55.61 microm and consisted of 81-229 layers. Cocooned claypan N. aquilonius were nearing exhaustion of their bladder water reserves and had a urine osmolality approaching that of the plasma. By contrast, non-cocooned N. aquilonius from the dune swale were fully hydrated, although soil moisture levels were not as high as calculated to be necessary to maintain water balance. Both species had similar plasma arginine vasotocin (AVT) concentrations ranging from 9.4 to 164 pg ml(-1), except for one cocooned N. aquilonius with a higher concentration of 394 pg ml(-1). For both species, AVT showed no relationship with plasma osmolality over the lower range of plasma osmolalities but was appreciably increased at the highest osmolality recorded. This study provides the first evidence that cocoon formation following burrowing is not obligatory in species that are capable of doing so, but that cocoon formation occurs when soil water conditions are more desiccating than for non-cocooned frogs.

Adaptation, Physiological↗
PubMed2001

Effects of hypoxia on egg capsule conductance in Ambystoma (Class Amphibia, Order Caudata).

Aquatic amphibian eggs frequently encounter hypoxic conditions that have the potential to limit oxygen uptake and thereby slow embryonic development and hatching. Oxygen limitation might be avoided if egg capsule surface area and oxygen conductance increased in response to hypoxia. We investigated this possibility in two salamander species, Ambystoma annulatum and Ambystoma talpoideum. The effective surface area of egg capsules increased in response to hypoxia, which increased the conductance for oxygen and enhanced oxygen transport. The ability of amphibian eggs to adjust their conductance in response to oxygen availability may increase survival in hypoxic environments.

Ambystoma↗
PubMed1975

Sperm concentration and fertilization rate in Bufo arenarum (Amphibia: Anura).

The influence of sperm concentration upon the fertilization rate of Bufo arenarum oocytes was determinated. The experimental results were analysed according to the theories of Rothschild and Swann, and Hultin and Hagström for Psammechinus miliaris. The experimental results agreed with the predictions of the latter theory. Since Bufo arenarum and Psammechinus miliaris oocytes differ in both size and disposition of jelly envelopes, the postulations of Hultin and Hagström's theory appear to have a general validity.

Animals↗
PubMedDate not supplied

Isolation and primary culture of Necturus maculosus (Amphibia: Urodela) hepatocytes.

In order to evaluate their suitability for physiological and ecotoxicological studies, hepatocytes were isolated from the common mudpuppy (Necturus maculosus) using a two-step collagenase perfusion. Hepatocytes in primary culture were investigated for 14 d using light and electron microscopy and biochemical analyses. A typical perfusion yielded 1.7 x 10(5) viable hepatocytes per gram body weight with an average viability of 86 +/- 5%. The majority of isolated cells remained in suspension and formed aggregates. The viability of hepatocytes in primary culture was dependent on a fetal calf serum (FCS) concentration and incubation temperature. Viability was best at 8 degrees C in Leibovitz L-15 medium supplemented with 5% FCS. The ultrastructural characteristics of freshly isolated hepatocytes resembled those of N. maculosus hepatocytes in vivo. Whereas hepatocyte viability remained relatively stable (around 80%) up to 14 d in culture, electron microscopic analyses revealed changes at ultrastructural level. The majority of hepatocytes retained similar structural characteristics to those in vivo up to 4 d. Loss of cellular polarity, fractionation of rough endoplasmic reticulum, formation of autophagosomes, and successive exhaustion of cellular glycogen deposits were observed with increased time in culture. Functional integrity, as estimated by tyrosine aminotransferase induction, decreased during the culture period. Ultrastructural and biochemical analyses indicate the need for further improvement of culture conditions. Nevertheless, isolated hepatocytes in primary culture for up to 4 d can be recommended as a model for physiological and toxicological studies in lower vertebrates.

Animals↗
PubMed1996

An immunohistochemical study on the innervation of two peptidergic (NPY and VIP) nerves in the cerebral arterial tree and choroid plexus of the newt (Amphibia: Urodela).

The pattern of neuropeptide Y (NPY)- and vasoactive intestinal polypeptide (VIP)-immunoreactive (IR) innervation was investigated in the cerebral arterial tree and choroid plexus of the newt by the use of an indirect immunofluorescence technique combined with chemical sympathectomy (6-OHDA). The data presented here, in conjunction with histochemical data reported previously, showed the following characteristic features of cerebrovascular innervation in this urodelan species. (1) The cerebral arterial tree and choroid plexus had unbalanced NPY-IR and VIP-IR innervation, characterized by the absence or a markedly lesser density of VIP-IR nerves. (2) All or nearly all of the NPY-IR nerves were sympathetic in nature. (3) A few cerebral perivascular NPY-IR nerves in some individuals originated from the sympathetic NPY-IR nerve cells intrinsic to the major cerebral arteries of the anterior circulatory system. (4) Acetylcholinesterase-positive neurons lacking both NPY and VIP immunoreactivities are a major nerve type in cerebrovascular parasympathetic innervation. The preferential NPY-IR innervation of the plexus microvascular-epithelial regions must be considered in relation to its special functions, such as the regulation of microcirculation, and cerebrospinal fluid (CSF) production and transportation. CSF is vital for the movement of nutrients and metabolites in the newt brain.

Acetylcholinesterase↗
PubMed1988

The first sequenced normal hemoglobin lacking histidine in position 146 of the beta-chains. The primary structures of the major and minor hemoglobin components of the great crested newt (Triturus cristatus, Urodela, Amphibia).

The hemoglobin of the Great Crested Newt (Triturus cristatus), an animal maintaining the gas exchange to about 85% through the skin, consists of a major (HbM = 65%) and a minor (Hbm = 35%) component. The primary structures of the four chains are presented. They could be separated by reversed-phase HPLC and were cleaved with trypsin and additionally by acid hydrolysis. Both the native chains and their peptides were sequenced by liquid and gas phase sequenators. At the N-terminus the alpha M-chains are by one amino-acid residue longer and the beta M-chains by one residue shorter, resulting in a chain length of 142 and 145, respectively. The alpha m-chains are of normal length whereas in the beta m-chains the C-terminal histidine in position 146 is missing. Both alpha-chains differ by 50 residues (35.2%) and the beta-chains by 63 (43.2%). The alpha-chains were compared with those of other salamandroid hemoglobins. The difference to human hemoglobin is marked by 61 (43.3%) amino-acid substitutions in both alpha-chains and by 78 (53.4%) in both beta-chains. Numerous heme contacts and positions involved in the subunit interface are affected by replacements. The most interesting of them were studied by molecular modeling. The importance of the missing beta m-146(HC3)His and of the substitution of several amino-acid residues involved in the binding of organic phosphates is discussed with respect to the reduced Bohr effect of Triturus cristatus hemoglobin.

Amino Acid Sequence↗
PubMed1978

[Phylogenetic studies on some Japanese amphibia by means of immunoelectrophoresis. II. Relationships of some amphibians to Japanese pond frogs (author's transl)].

Since the Japanese pond frogs (Rana nigromaculata and R. brevipoda) are known to be very closely allied with each other in morphological, ecological, physiological or immunological characters, the phylogenetical relationships between the Japanese pond frogs and other 10 species of Japanese amphibians were investigated by means of immunoelectrophoretic analysis of liver extract. The results obtained are as follows: (1) There are conservative antigens which are commonly found in all species of Anura. (2) The Japanese pond frogs have specific antigens. (3) R. nigromaculata and R. brevidpoda are very closely allied with each other. (4) Four species of the genus Rana (R. rugosa, R. catesbeiana, R. ornativentris and R. japonica) are closely related to the Japanese pond frogs. (5) Two species of the genus Rhacophorus (Rh. arboreus and Rh. burergeri) are related to the Japanese pond frogs. (6) R. limnocharis is related to the Japanese pond frogs at the same extent as the genus Rhcophorus is. (7) Tow species of the suborder Procoela (Hyla arbored and Bufo bufo) are only partially related to the Japanese pond frogs. (8) Cynops pyrrhogaster pyrrhogaster of Urodera had only a few common antigens with the Japanese pond frogs.

Amphibians↗