Biomedical subjects

Jean M P Joss

Publications and source records attributed to Jean M P Joss.

15 recordsLinked to original sources

PubMed2006

Embryonic gonadal and sexual organ development in a small viviparous skink, Niveoscincus ocellatus.

The majority of research into the timing of gonad differentiation (and sex determination) in reptiles has focused on oviparous species. This is largely because: (1) most reptiles are oviparous; (2) it is easier to manipulate embryonic developmental conditions (e.g., temperature) of eggs than oviductal embryos and (3) modes of sex determination in oviparous taxa were thought to be more diverse since viviparity and environmental sex determination (ESD)/temperature-dependent sex determination (TSD) were considered incompatible. However, recent evidence suggests the two may well be compatible biological attributes, opening potential new lines of enquiry into the evolution and maintenance of sex determination. Unfortunately, the baseline information on embryonic development in viviparous species is lacking and information on gonad differentiation and sexual organ development is almost non-existent. Here we present an embryonic morphological development table (10 stages), the sequence of gonad differentiation and sexual organ development for the viviparous spotted snow skink (Niveoscincus ocellatus). Gonad differentiation in this species is similar to other reptilian species. Initially, the gonads are indifferent and both male and female accessory ducts are present. During stage 2, in the middle third of development, differentiation begins as the inner medulla regresses and the cortex thickens signaling ovary development, while the opposite occurs in testis formation. At this point, the Müllerian (female reproductive) duct regresses in males until it is lost (stage 6), while females retain both ducts until after birth. In the later stages of testis development, interstitial tissue forms in the medulla corresponding to maximum development of the hemipenes in males and the corresponding regression in the females.

Animals↗

PubMed2005

Lungfish evolution and development.

The first vertebrates recognizable as tetrapods appeared in the mid-Devonian. It is generally agreed that their ancestors were lobe-finned fish. What is not agreed is how close either of the extant groups of lobe-finned fish, lungfish or coelacanths, is to the actual ancestor of the tetrapods. The soft anatomy of living lungfish shares many similarities with that of living amphibians. Many of these similarities are not present in either coelacanths or any members of the other extant bony fish group, the ray-finned fishes. Many very well preserved lungfish from the Devonian possess specialized features that would appear to exclude them from being ancestral to tetrapods. I am hypothesizing that lungfish in the Devonian may have included metamorphosis in their life cycle and that neoteny in some species may have been an early corollary. These reproductively mature neotenous lungfish would not have had the specialised features of metamorphosed adults. Fossils of these neotenous forms may have more closely resembled the tetrapod ancestral lobe-finned fish, currently believed to be a panderichthiad fish. Living lungfish have a number of larval features, which suggest paedomorphosis. Also of significance is the very large genome of living lungfish, which, in urodele amphibians, is a feature correlated with neoteny. Our current knowledge of the thyroid axis in the lungfish, Neoceratodus forsteri, is consistent with neoteny in amphibians, but the only Devonian fossil considered to be a larval lungfish bears no resemblance to living lungfish or to panderichthiads. The enigmatic phylogenetic relationship of lungfish with the first tetrapods remains, but the hunt for other forms of larval Devonian lungfish is on!

Animals↗

PubMed2005

Occurrence of two functionally distinct proopiomelanocortin genes in all modern lampreys.

The lampreys (family Petromyzontidae) are divided into three subfamilies, the Petromyzontinae in the Northern Hemisphere and the Geotriinae and Mordaciinae in the Southern Hemisphere. We previously found two proopiomelanocortin subtypes, proopiocortin (POC) and proopiomelanotropin (POM) in sea lamprey, Petromyzon marinus (Petromyzontinae). POC encoding adrenocorticotropic hormone (ACTH) and beta-endorphin (beta-END) is expressed in the pars distalis of the pituitary, while POM encoding melanophore-stimulating hormone (MSH)-A and B together with a different beta-END is expressed in the pars intermedia of the pituitary. All these hormonal segments are encoded on the third exon in both POC and POM. Here, we demonstrate the presence of both POC and POM genes in Geotria australis (Geotriinae) and Mordacia mordax (Mordaciinae) by molecular cloning of the third exons with the polymerase chain reaction using genomic DNA or pituitary cDNA. Molecular phylogenetic analysis showed that the POC and POM are distinctly different for the Southern Hemisphere lampreys as they are for P. marinus. Moreover, the relationship of each hormonal segments in POC and POM between Geotria, Mordacia, and Petromyzon is inconsistent. Immunocytochemical studies showed that the distribution of POC and POM in the pituitaries of the Southern Hemisphere lampreys is the same as that in the Northern Hemisphere. Taken together, these findings suggest that the duplication event which generated the two genes may have occurred in a common ancestor of the three extant lamprey subfamilies.

Amino Acid Sequence↗

PubMed2005

NfCR1, the first non-LTR retrotransposon characterized in the Australian lungfish genome, Neoceratodus forsteri, shows similarities to CR1-like elements.

The genomes of lungfish, together with those of some urodele amphibians, are the largest of all vertebrate genomes. It has been assumed that the bulk of the DNA making up these large genomes has been derived from repeat elements, like the noncoding DNA of those genomes that have been sequenced (e.g., human). In an attempt to characterize repeat sequences in the lungfish genome, we have isolated, by restriction enzyme digestion of genomic DNA, sequences of a repeat element in Neoceratodus forsteri, the most primitive of the living lungfishes. The fragments sequenced from the EcoRI and BglII digests were used to perform genome walking PCR in order to obtain the full sequence of the repeat element. This element shares homology with the non-LTR (LINE) element, Chicken Repeat 1 (CR1), described for several vertebrates and some invertebrates; we have called it N. forsteri CR1 (NfCR1). NfCR1 shares all the domains of other CR1 elements but it also has several unique features that suggest it may no longer be active in the lungfish genome. It occurs in both full-length and 5'-truncated versions and in its present "inactive" form represents approximately 0.05% of the lungfish genome.

Amino Acid Sequence↗

PubMed2004

Cloning of prodynorphin cDNAs from the brain of Australian and African lungfish: implications for the evolution of the prodynorphin gene.

In mammals the opioids Met-enkephalin and Leu-enkephalin are derived from a common precursor, proenkephalin, and as a result these neuropeptides are co-localized in enkephalinergic neurons. The mammalian scheme for enkephalinergic networks is not universal for all classes of sarcopterygian vertebrates. In an earlier study, distinct Met- and Leu-enkephalin-positive neurons were detected in the central nervous system (CNS) of the African lungfish, Protopterus annectens. More recently, characterization of proenkephalin cDNAs separately cloned from the CNS of P. annectens and the Australian lungfish, Neoceratodus forsteri, revealed that the proenkephalin gene in these species encodes only Met-enkephalin-related opioids. In the current study a full-length prodynorphin cDNA (accession No. AY 445637) was cloned and sequenced from the CNS of N. forsteri. In addition to encoding alpha-neoendorphin, dynorphin A and dynorphin B sequences unique to the lungfish, two Leu-enkephalin sequences, flanked by paired basic amino acid proteolytic cleavage sites, were detected in this precursor. The partial sequence of a P. annectens prodynorphin cDNA (accession No. AY445638) also encoded a Leu-enkephalin sequence and a novel YGGFF sequence. The presence of the Leu-enkephalin sequence in the lungfish prodynorphin precursors would explain the origin of the distinct Leu-enkephalin-positive neurons found in the African lungfish CNS. The realization that Met-enkephalin and Leu-enkephalin can be derived from distinct opioid-coding precursor genes calls into question the interpretation of comparative immunohistochemical studies that have mapped 'enkephalinergic' networks in non-mammalian vertebrates.

Africa↗

PubMed2004

Maternal basking behaviour determines offspring sex in a viviparous reptile.

Two primary dichotomies within vertebrate life histories involve reproductive mode (oviparity versus viviparity) and sex determination (genotypic sex determination versus environmental sex determination). Although reptiles show multiple evolutionary transitions in both parameters, the co-occurrence of viviparity and environmental-dependent sex determination have heretofore been regarded as incompatible. Our studies on the viviparous lizard Niveoscincus ocellatus show that the extent of basking by a female influences the sex of her offspring. Critically, our data reveal this effect both in the field (via correlations between date of birth and litter sex ratio) and in a laboratory experiment (females with reduced basking opportunities produced more male offspring). Changes in thermoregulatory behaviour thus allow pregnant female lizards to modify the sex of their offspring.

Animals↗

PubMed2004

Identification of angiotensin I in several vertebrate species: its structural and functional evolution.

In order to delineate further the molecular evolution of the renin-angiotensin system in vertebrates, angiotensin I (ANG I) has been isolated after incubation of plasma and kidney extracts of emu (Dromiceus novaehollandiae), axolotl (Ambystoma mexicanum), and sea lamprey (Petromyzon marinus). The identified sequences were [Asp1, Val5, Asn9] ANG I in emu, [Asp1, Val5, His9] ANG I in axolotl, and [Asn1, Val5, Thr9] ANG I in sea lamprey. These results confirmed the previous findings that tetrapods have Asp and fishes including cyclostomes have Asn at the N-terminus, and that the amino acid residue at position 9 of ANG I was highly variable but, those at other positions were well conserved among different species. Since Asp and Asn are convertible during incubation, angiotensinogen sequences were searched in the genome and/or EST database to determine the N-terminal amino acid residue from the gene. The screening detected 12 tetrapod (10 mammalian, one avian, and one amphibian) and seven teleostean angiotensinogen sequences. Among them, all tetrapods have [Asp1] ANG except for Xenopus, and all teleosts have [Asn1] ANG, thereby confirming the above rule. Comparison of the vasopressor activity in the eel revealed that [Asn1] ANG I and II were more potent than [Asp1] peptides, which was opposite to the previous results in mammals and birds, in which [Asp1] ANG I and II were more potent. Collectively, the present results support the general rule that tetrapods have [Asp1] ANG and fishes including cyclostomes have [Asn1] ANG. However, an aquatic anuran (Xenopus) has [Asn1] ANG in its gene despite another aquatic urodele (axolotl) has [Asp1] ANG. From the functional viewpoint, homologous [Asn1] ANG was more potent in fish as is homologous [Asp1] ANG in tetrapods, suggesting that ANG II molecule has undergone co-evolution with its receptor during vertebrate phylogeny.

Ambystoma↗

PubMed2004

Deiodinase type III in the Australian lungfish, Neoceratodus forsteri.

This work presents characterisation of deiodinase type III (D3) mRNA as cDNA and the tissue distribution of D3 mRNA in the Australian lungfish, Neoceratodus forsteri. We have identified the full length of a approximately 1.4 kb D3 mRNA in the liver, which has a single in-frame UGA codon and a selenocysteine insertion sequence (SECIS) form 2 in the 3'-UTR. Lungfish D3 mRNA was expressed in all tested tissues (liver, lung, kidney, brain, heart, and gills) as demonstrated by Northern blot analyses. PCR conducted on genomic DNA indicated that the lungfish D3 is a single exon gene. Also, we present enzymatic characteristics of this exclusively IRD enzyme, have determined its substrate preference, DTT cofactor requirements, PTU inhibition, and kinetic properties. These results indicate that lungfish D3 has the typical enzymatic characteristics of vertebrate D3 enzymes.

Amino Acid Sequence↗

PubMed2004

The scapulocoracoid of the Queensland lungfish Neoceratodus forsteri (Dipnoi: Sarcopterygii): morphology, development and evolutionary implications for bony fishes (Osteichthyes).

Among bony fishes, the ontogenetic sequence by which the actinopterygian scapulocoracoid develops has been well described, but that of the sarcopterygian scapulocoracoid is poorly known, as the majority of taxa are only known from fossils. To rectify this, the cartilaginous scapulocoracoid of the extant lungfish Neoceratodus forsteri is examined. In initial stages of its development, the scapulocoracoid of Neoceratodus has a simple rounded shape, and supports the glenoid fossa. It appears nearly contemporaneously with the proximal endochondral element (humerus) of the pectoral fin. Pectoral fin elements develop by segmentation from a continuous field of cartilaginous precursor cells extending distally from the glenoid region of the scapulocoracoid. Subsequent scapulocoracoid development produces a ventromedial process, which is not associated with this field of precursor cells. A dorsal process also develops outside this field. Thus, the scapulocoracoid of Neoceratodus may consist of at least two developmentally distinct regions; (1) the ventromedial being homologous with the coracoid of actinopterygians, tetrapods and other jawed vertebrates and (2) a smaller dorsal process, homologous to the scapular region. The two, together with the glenoid region, give an overall triangular shape. The scapulocoracoids of fossil lungfish and other sarcopterygian fishes are also triangular and are composed of scapular and coracoid regions, rather than the 'buttresses' associated with scapulocoracoids of the Actinopterygii and Tetrapoda.

Journal Article↗

PubMed2003

Pituitary glycoprotein hormone beta subunits in the Australian lungfish and estimation of the relative evolution rate of these subunits within vertebrates.

The beta subunits of the two pituitary gonadotropins LH and FSH and of thyroid-stimulating hormone (TSH) were cloned from Australian lungfish (Neoceratodus forsteri) pituitary glands. These three glycoprotein hormone beta subunits possess the main characteristics common to their counterparts in other vertebrates. Taking advantage of the phylogenetic position of the lungfish, close to the root of tetrapods, a maximum parsimony tree was inferred from these new sequences and sequences from representatives of the diversity of vertebrates. The topology of the tree was imposed so that it reflected as closely as possible the real evolutionary history of the subunits. This tree was used to estimate the relative evolution rate of the three subunits in vertebrates. Cumulated amino acid substitutions from the basal subunit node (ancestral subunit sequence) to the species node were calculated and compared. It showed that a burst in evolutionary rate occurred for the LHbeta subunit in the tetrapod lineage sometime after the emergence of amphibians. The rate of evolution of the LHbeta subunit was particularly high throughout the radiation of mammals while FSH and TSHbeta subunits kept quite stable in this lineage. A burst in evolutionary rate was also observed for the FSHbeta subunit in the lineage leading to teleosts sometime after the emergence of chondrosteans and the dynamic of evolution was high throughout the radiation of teleosts. These results were consistent with data obtained from pairwise comparisons.

Amino Acid Sequence↗

PubMed2003

Keratinization of the epidermis of the Australian lungfish Neoceratodus forsteri (dipnoi).

The differentiation of the epidermis in sarcopterigian fish may reveal some trend of keratinization followed by amphibian ancestors to adapt their epidermis to land. Therefore, the process of keratinization of the epidermis of the Australian lungfish Neoceratodus forsteri was studied by histochemistry, electron microscopy, and keratin immunocytochemistry. The epidermis is tri-stratified in a 2-3-month-old tadpole but becomes 6-8 stratified in young adults. Keratin filaments increase from basal to external cells where loose tonofilament bundles are present. This is shown also by the comparison of positivity to sulfhydryl groups and increasing immunoreactivity to alpha-keratins in more external layers of the epidermis. Two broad-spectrum anti alpha-keratin monoclonal antibodies (AE1 and AE3) stain all epidermal layers as they do in actinopterigian fish. In the adult epidermis, but not in that of the larva, the AE2 antibody (a marker of keratinization in mammalian epidermis) often immunolabels more heavily the external keratinized layers where sulfhydryl groups are more abundant. Mucous granules are numerous and concentrate on the external surface of the epidermis to be discharged and contribute to cuticle formation. Keratin is therefore embedded in a mucus matrix, but neither compact keratin masses nor cell corneous envelope were seen in external cells. It is not known whether specific matrix proteins are associated with mucus. There was no immunolocalization of the keratin-associated proteins, filaggrin and loricrin, which suggests that the epidermis of this species lacks the matrix and cell corneus envelope proteins characteristic of that of amniotes. In conclusion, while specific keratins (AE2 positive) are probably produced in the uppermost layers as in amphibian epidermis, no interkeratin, matrix proteins seem to be present in external keratinocytes of the lungfish other than mucus.

Aging↗

PubMed2003

Deiodinase type II and tissue specific mRNA alternative splicing in the Australian lungfish, Neoceratodus forsteri.

Deiodinase type II metabolises the prohormone T4 (thyroxine) into the biologically active hormone T3 (3,5,3'-triiodothyronine), at the cellular level in extrathyroidal target tissues. In juvenile lungfish, Neoceratodus forsteri, a typical deiodinase type II is present in most tissues. We have identified the full length of a 1.8 kb deiodinase type II mRNA in liver, and a truncated (1.3 kb) version in brain. Both mRNAs have two in frame UGA codons, but only the liver form has a predicted SECIS structure (form 1) in its 3'-UTR. We also report the presence of additional different length transcripts of deiodinase II mRNA, i.e., 3, 4, and 8 kb, in liver, and 8 kb in kidney, heart, and gill tissues. Expression of the longer (approximately 8 kb) transcript is very low. Real-time PCR confirmed the low expression of transcripts in all tissues, suggested by the Northern blot analysis.

Alternative Splicing↗

PubMed2003

Structure and function of visual displays produced by male jacky dragons, Amphibolurus muricatud, during social interactions.

Many lizards produce visual displays to mediate social behavior. However, most studies have focused upon displays used by iguanid lizards. We investigated and quantified the displays used by jacky dragons, an agamid lizard from southeastern Australia. By establishing male jacky dragons within individual territories and conducting experimental presentations of male and female intruders, we were able to demonstrate that territorial male Amphibolurus muricatus utilize a fixed action pattern display comprising discrete motor components to indicate territoriality and aggression. Displays directed to intruders contain an extra introductory component and modifying postural elements, whereas non-directed displays given in the absence of intruders lack these features and appear to be used to advertise territory ownership. Although the sequence of display components remained the same across non-directed, male-directed and female-directed displays, resident males differed in pushup duration and the number of pushups per display in relation to individual body size. This display variance might function to provide an honest signal revealing the body size or the physical condition of each individual, permitting opponents to assess each other effectively through their displays. Visual signals produced by intruding lizards were qualitatively distinct from the displays given by residents, and appear to indicate submission. However, male and female intruders differed in the frequency with which each type of submissive gesture was performed, implying that this might convey intruder sex.

Animals↗

PubMed2003

Steroid correlates of territorial behavior in male jacky dragons, Amphibolurus muricatus.

Male jacky dragons, Amphibolurus muricatus, indicate territoriality to rivals during the mating season through the use of stereotyped motor displays. The relationship between corticosterone (B) and testosterone (T) and its effects on territorial display expression were investigated in captive lizards. Results demonstrated that territorial display production was most effectively predicted by elevated baseline T levels. This parallels the heightened T concentrations exhibited by males in the field during the spring mating period. The effect of social interaction on B and T levels was also examined by presenting territory-holding males with a size-matched male intruder. Resident males exhibited clear differences in the level of territorial response evoked by a male intruder, which were correlated with differences in physiological activity. Males that gave no territorial response had moderate B levels that did not change with social interaction, and significantly lower T levels than males that responded to the intruder with territorial displays. Among displaying males, those exhibiting low levels of territorial responses showed no change in B or T. In contrast, high-level territorial responders exhibited acute B increases when faced with an intruder, which might assist in supporting sustained metabolic activity and could possibly reflect differences in the perception of social stress. These same males also exhibited a reduction in T levels at such times, probably due to the acute rise in B. Combined, these results suggest that high circulating T is acting in a preparatory manner to increase the likelihood of producing a territorial response upon engaging in a social encounter. However, once this response has been initiated T may not need to remain elevated to allow continued expression of territorial behavior.

Aggression↗

PubMed2002

Purification, characterization, and biological activity of a substance P-related peptide from the gut of the Australian lungfish, Neoceratodus forsteri.

A peptide with mammalian substance P (SP)-like immunoreactivity was isolated from an extract of the spiral intestine of the Australian lungfish, Neoceratodus forsteri. The primary structure of this peptide was established as Lys-Pro-Arg-Pro-Asp-Glu-Phe-Tyr-Gly-Leu-Met . NH2, showing 64% identity with mammalian SP. In isolated preparations of lungfish foregut circular muscle, lungfish SP produced a slow, long-lasting tonic contraction, with a pD2 value of 8.19. Lungfish midgut circular muscle preparations responded to lungfish SP rapidly and in a more complex manner. There was an increase in the frequency of spontaneous activity (pD2 = 8.76), associated with diminished amplitude of the spontaneous contractions (pD2 = 9.24), also coupled in some preparations with a tonic contraction (pD2 = 8.43). The response patterns of foregut and midgut circular muscle to acetylcholine (ACh) were very similar to those seen to lungfish SP. Lungfish SP and ACh, however, had very weak effects on both foregut and midgut longitudinal muscle. These data demonstrate that lungfish SP may be a physiologically important regulator of gastrointestinal motility in Neoceratodus. This study further confirmed that the structures of SP-related peptides have been strongly conserved under the pressure of vertebrate evolution, particularly in preserving the functionally important sequence, Phe-Xaa-Gly-Leu-Met . amide, at the C-terminus. The sequence of lungfish SP is identical to that of bufokinin, a SP-related peptide previously isolated from the intestine of the cane toad, Bufo marinus, supporting the hypothesis that lungfishes and amphibians share a common ancestor.

Acetylcholine↗