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D M Power

Publications and source records attributed to D M Power.

At least 37 records · Page 2Linked to original sources
PubMed2002

Calcitonin: characterisation and expression in a teleost fish, Fugu rubripes.

The present report describes the structure and expression of the calcitonin gene in Fugu rubripes. It is composed of 4 exons and 3 introns. Splicing of exons 1, 2 and 3 generates the calcitonin pre-proprotein, while splicing of exons 1, 2 and 4 generates calcitonin gene-related protein (CGRP). Exons 1 and 2 encoding the signal sequence and the N-terminal peptide are common in both the gene products and this gene organisation has been conserved in human, rat, chicken and salmon. The gene environment around calcitonin in Fugu has been poorly conserved when compared with human, apart from a small gene cluster. The calcitonin gene in Fugu has a widespread tissue distribution but it is most highly expressed in the brain. The abundance of gene expression in the ultimobranchial gland and the pituitary indicates that these are important sites of production and that the peptide is probably secreted into the circulation and/or acts as a paracrine or autocrine controlling factor. Whilst the function of calcitonin in fish is still largely unknown, the distribution described here suggests that one of the potential functions may be as a neuropeptide.

Amino Acid Sequence↗
PubMed2002

Calcium balance in sea bream (Sparus aurata): the effect of oestradiol-17beta.

In all teleost fishes vitellogenesis is triggered and maintained by oestradiol-17beta (E2) and is accompanied by an increase of blood plasma calcium and phosphate. The action of this hormone on calcium metabolism was investigated by treating fast-growing immature juvenile sea bream (Sparus aurata) with coconut butter implants alone (control) or implants containing 10 microg/g E2. Treatment with E2 induced the production of circulating vitellogenin, a 2.5-fold increase in plasma ionic Ca2+ and a 10-fold increase in plasma total calcium, largely bound to protein. In contrast to freshwater species, which obtain most of their calcium from the environment directly through the gills, the intestinal component of calcium uptake of the salt water-living sea bream represented up to 60-70% of the total uptake. The whole body calcium uptake, expressed as the sum of calcium obtained via intestinal and extra-intestinal (likely branchial) routes increased significantly in response to E2. Combined influx and unchanged efflux rates resulted in a significant 31% increase in net calcium uptake. There was no evidence for an effect of E2 on the calcium and phosphate content of the scales or the tartrate-resistant acid phosphatase activity (an index for bone/scale osteoclast activity). While most freshwater fish appear to rely on internal stores of calcium, i.e. bone and/or scales to increase calcium availability, the marine sea bream accommodates calcium-transporting mechanisms to obtain calcium from the environment and preserve internal stores. These observations suggest that a fundamental difference may exist in the E2-dependent calcium regulation between freshwater and marine teleosts.

Acid Phosphatase↗
PubMed2001

Cloning, characterization, and tissue distribution of prolactin receptor in the sea bream (Sparus aurata).

The prolactin receptor (PRLR) was cloned and its tissue distribution characterized in adults of the protandrous hermaphrodite marine teleost, the sea bream (Sparus aurata). An homologous cDNA probe for sea bream PRLR (sbPRLR) was obtained by RT-PCR using gill mRNA. This probe was used to screen intestine and kidney cDNA libraries from which two overlapping clones (1100 and 2425 bp, respectively) were obtained. These clones had 100% sequence identity in the overlapping region (893 bp) and were used to deduce the complete amino acid sequence of sbPRLR. The receptor spans 2640 bp and encodes a protein of 537 amino acids. Features characteristic of PRLR, two pairs of cysteines, WS box, hydrophobic transmembrane domain, box 1, and box 2, were identified and showed a high degree of sequence identity to PRLRs from other vertebrate species. SbPRLR is 29 and 32% identical to tilapia (Oreochromis niloticus) and goldfish (Carassius auratus) PRLRs, respectively. In the sea bream two PRLR transcripts of 2.8 and 3.2 kb were detected in the intestine, kidney, and gills and a single transcript of 2.8 kb was detected in skin and pituitary by Northern blot. Spermiating gonads (more than 95% male tissue; gonado-somatic index of 0.6) contained, in addition to the 2.8-kb transcript, three more transcripts of 1.9, 1.3, and 1.1 kb. RT-PCR, which is a far more sensitive method than Northern blot, detected PRLR mRNA in gills, intestine, brain, pituitary, kidney, liver, gonads, spleen, head-kidney, heart, muscle, and bone. Immunohistochemistry using specific polyclonal antibodies raised against an oligopeptide from the extracellular domain of sbPRLR detected PRLR in several epithelial tissues of juvenile sea bream, including the anterior gut, renal tubule, choroid membrane of the third ventricle, saccus vasculosus, branchial chloride cells, and branchial cartilage.

Amino Acid Sequence↗
PubMed2001

Characterization of a sea bream (Sparus aurata) thyroid hormone receptor-beta clone expressed during embryonic and larval development.

A clone encoding thyroid hormone receptor-beta (TR-beta) was isolated from a sea bream (Sparus aurata) ovary cDNA library. Sea bream (sb)TR-beta is closely related to its counterparts from other vertebrates and, like them, preferentially binds T3 rather than T4. However, the putative sbTR-beta protein contains a nine-amino-acid insert that is also present in the corresponding proteins from flounder and salmon but absent in TR-betas from zebrafish and terrestrial vertebrates. Semiquantitative RT-PCR analysis showed that sbTR-beta transcripts begin to accumulate during gastrulation and increase markedly in quantity up to the period around hatch (ca. 40 h postfertilization) before declining slightly. In adult tissues, TR-beta mRNA was present in approximately equal quantities in heart, intestine, brain, kidney, skeletal muscle, liver, and gill. The significance of the relatively strong expression of TR-beta during sea bream embryogenesis is discussed.

Amino Acid Sequence↗
PubMed2001

Molecular cloning and sequence of gilthead sea bream (Sparus aurata) alpha-skeletal actin: tissue and developmental expression.

In the present study, the Sparus aurata alpha-skeletal actin was cloned from a mixed larvae complementary DNA library. The clone isolated was 1523 bp long with an open reading frame of 1134 bp coding for a 377-amino acid protein. The deduced amino acid sequence of sea bream alpha-actin is identical to Fugu alpha-actin-1. The expression of alpha-actin was initiated at the onset of segmentation. In adult fish, alpha-actin is expressed predominantly in white and red muscle.

Actins↗
PubMed2001

Thyroid hormones in growth and development of fish.

The thyroid hormones (THs), thyroxine (T(4)) and triiodothyronine (T(3)) are products of the thyroid gland in all vertebrates. Their role in early development and metamorphosis is well established in mammals and amphibians, respectively, and recently several studies in fish have highlighted the importance of THs during flatfish metamorphosis. THs are present in high quantities in fish eggs and are presumably of maternal origin. During embryogenesis the concentration of T(4) and T(3) in the eggs decrease until endogenous production starts. Thyroid hormone receptors (TR) have been isolated from several teleosts and in common with tetrapods two receptor isoforms have been identified, TR alpha and TR beta. Both the receptors are expressed in early embryos and larvae of the Japanese flounder (Paralichthys olivaceus), zebrafish (Danio rerio) and seabream (Sparus aurata) although a different temporal pattern is apparent. The role of THs and TRs in fish embryogenesis, larval development and during metamorphosis will be discussed.

Amino Acid Sequence↗
PubMed2001

Parathyroid hormone-related protein: a calcium regulatory factor in sea bream (Sparus aurata L.) larvae.

The effects of an N-terminal peptide (amino acids 1-38) of Fugu parathyroid hormone-related protein (PTHrP 1-38) on calcium regulation of larval sea bream were investigated in seawater (36 per thousand) and after transfer to dilute seawater (12 per thousand). Exposure to PTHrP 1-38 evoked a 1.5-fold increase in calcium influx in both full-strength and dilute seawater. Calcium influx in dilute seawater-adapted larvae was roughly one-half that observed in full-strength seawater controls. PTHrP 1-38 also reduced drinking of fish in seawater but, at all concentrations tested, was without effect in dilute seawater. The amount of water imbibed was 55% lower in dilute seawater than in seawater. PTHrP 1-38 exposure affected the calcium influx route: the main contribution of calcium uptake shifted from intestinal absorption to extraintestinal uptake, probably by the induction of a dose-dependent increase in branchial (active) transport. Moreover, seawater-adapted fish exposed to 1 nM and 10 mM PTHrP 1-38 experienced a 2.5-fold reduction in overall calcium efflux. Overall, the calciotropic action of PTHrP 1-38 resulted in a dose-dependent increase in net calcium balance.

Adaptation, Physiological↗
PubMed2001

Molecular cloning and sequence of Sparus aurata skeletal myosin light chains expressed in white muscle: developmental expression and thyroid regulation.

Two full-length cDNA clones encoding the skeletal myosin light chain 2 (MLC2; 1452bp) and myosin light chain 3 (MLC3; 972bp) were isolated from a cDNA library prepared from gilthead sea bream Sparus aurata larvae. The MLC2 cDNA encoded a predicted protein of 170 residues that was 79% identical to rabbit MLC2 over the entire length and 87% identical within the Ca(2+)-binding region. The deduced amino acid sequence of MLC3 was 153 residues in length and was 91% and 69% identical to the zebrafish and rabbit MLC3, respectively. Northern blot analysis revealed that in adults both transcripts were expressed in fast white muscle only. MLC2 appeared earlier in development: MLC2 transcripts were detectable from the beginning of segmentation, whereas MLC3 transcripts did not appear until 27h post-fertilisation. At this developmental stage, a second MLC2 transcript of 0.89 kilobase-pairs was present. MLCs exhibited a different age-related pattern of response to varied thyroidal states, which were experimentally induced by the administration of 1 microg g(-1)body mass of thyroxine (T4) or triiodothyronine (T3), or 5 ng g(-1)body mass of the hypothyroidal compound thiourea; MLC3 expression was not significantly affected, whereas levels of MLC2 transcripts were significantly elevated in the white muscle only of juvenile sea bream after administration of T4. Although the mechanism of thyroidal regulation of MLC expression remains unknown, the present results suggest that different regulatory mechanisms exist for different MLCs.

Amino Acid Sequence↗
PubMed2000

Genomic structure and expression of parathyroid hormone-related protein gene (PTHrP) in a teleost, Fugu rubripes.

In this study we describe the isolation and characterisation of the parathyroid hormone-related protein (PTHrP) gene from the teleost Fugu rubripes. The gene has a relatively simple structure, compared with tetrapod PTHrP genes, composed of three exons and two introns, encompassing 2.25kb of genomic DNA. The gene encodes a protein of 163 amino acids, with a putative signal peptide of 37 amino acids and a mature peptide of 126 amino acids. The overall homology with known tetrapod PTHrP proteins is low (36%), with a novel sequence inserted between positions 38 and 65, the absence of the conserved pentapeptide (TRSAW) and shortened C-terminal domain. The N-terminus shows greater conservation (62%), suggesting that it may have a hypercalcaemic function similar to that of tetrapod PTHrP. In situ localisation and RT-PCR have demonstrated the presence of PTHrP in a wide range of tissues with varying levels of expression. Sequence scanning of overlapping cosmids has identified three additional genes, TMPO, LDHB and KCNA1, which map to human chromosome 12, with the latter two mapping to 12p12-11.2. PTHrP in human also maps to this chromosome 12 sub-region, thus demonstrating conservation of synteny between human and Fugu.

Amino Acid Sequence↗
PubMed2000

Cloning of the cDNA for sea bream (Sparus aurata) parathyroid hormone-related protein.

This paper reports cloning of the cDNA for sea bream (Sparus aurata) parathyroid hormone-related protein (PTHrP). The gene codes for a 125-amino acid mature protein with a 35-residue prepeptide. The total gene sequence is 1.8 kb with approximately 75% noncoding. The N-terminus of the protein resembles mammalian and chicken PTHrP peptides with 12 of the first 21 amino acids identical and for which there is homology with mammalian parathyroid hormone. Toward the C-terminus, the nuclear transporter region between residues 79 and 93 in sea bream is 73% homologous to tetrapod PTHrP, and the RNA binding domain, 96-117, is 50% homologous, moreover starting with the conserved lysine and terminating with the lysine/arginine sequence. Sea bream PTHrP differs significantly from mammalian and chicken PTHrP, having a novel 16-amino acid segment between residues 38 and 54 and completely lacking the terminal domain associated in mammals with inhibition of bone matrix lysis. RT-PCR and in situ hybridization of sea bream tissues show that the gene is expressed widely and the results confirm observations of a PTHrP-like factor in sea bream detected with antisera to human PTHrP.

Amino Acid Sequence↗
PubMed2000

Evolution of the thyroid hormone-binding protein, transthyretin.

Transthyretin (TTR) belongs to a group of proteins, which includes thyroxine-binding globulin and albumin, that bind to and transport thyroid hormones in the blood. TTR is also indirectly implicated in the carriage of vitamin A through the mediation of retinol-binding protein (RBP). It was first identified in 1942 in human serum and cerebrospinal fluid and was formerly called prealbumin for its ability to migrate faster than serum albumin on electrophoresis of whole plasma. It is a single polypeptide chain of 127 amino acids (14,000 Da) and is present in the plasma as a tetramer of noncovalently bound monomers. The major sites of synthesis of TTR in eutherian mammals, marsupials, and birds are the liver and choroid plexus but in reptiles it is synthesised only in the choroid plexus. The observation that TTR is strongly expressed in the choroid plexus but not in the liver of the stumpy-tailed lizard and the strong conservation of expression in the choroid plexus from reptiles to mammals have been taken as evidence to suggest that extrahepatic synthesis of TTR evolved first. The identification and cloning of TTR from the liver of an amphibian, Rana catesbeiana, and a teleost fish, Sparus aurata, and its absence from the choroid plexus of both species suggest an alternative model for its evolution. Protein modelling studies are presented that demonstrate differences in the electrostatic characteristics of the molecule in human, rat, chicken, and fish, which may explain why, in contrast to TTR from human and rat, TTR from fish and birds preferentially binds triiodo-l-thyronine.

Amino Acid Sequence↗
PubMed2000

Radial scar.

Radial scars attract interest due to its mammographic appearance and pathology. It is still unclear whether it is a benign or premalignant condition. This article reviews the clinical feature, pathology and its relation to malignancy.

Journal Article↗
PubMed2000

Outcome from poor grade aneurysmal subarachnoid haemorrhage--which poor grade subarachnoid haemorrhage patients benefit from aneurysm clipping?

Patients with poor grade aneurysmal subarachnoid haemorrhage (SAH) are associated with high mortality and morbidity, and hence are often treated conservatively. This study has set out to determine the outcome for all poor grade subarachnoid haemorrhage patients, and attempts to identify a subgroup with a more favourable prognosis. During a prospective audit of patients with aneurysmal SAH, patients of poor grade [World Federation of Neurological Surgeons (WFNS) IV (and not obeying commands) and V] were sedated, paralysed and ventilated for transfer to the Regional Neurosurgical Unit. Any intraventricular blood and/or hydrocephalus was treated by external ventricular drainage. Following a 24-h period for active blood gas, fluid and electrolyte resuscitation, patients were assessed after reversal of sedation. Selection for angiography and potential aneurysm surgery was restricted to those who showed a purposeful response to painful stimulation. Patients who could readily obey commands were not considered 'true' poor grade and were excluded from analysis. In 102 patients with 'true' poor grade SAH admitted between 1991 and 1997, the overall management outcome at 6 months was poor (favourable outcome 25%, mortality 67%). Following reversal of sedation, 55 patients demonstrated a purposeful response and proceeded to angiography, of whom 37 underwent clipping and three coiling of aneurysm. The outcome in this aneurysm treated subgroup was favourable in 53% (mortality 28%). If patients over the age of 65 years are excluded, the management outcome was favourable in 35% (mortality 58%), with those patients proceeding to clipping or coiling of aneurysms having a favourable outcome in 57% (mortality 27%). Patients over the age of 65 years with poor grade SAH had a favourable outcome in only 6% (mortality 85%). The mortality for poor grade SAH patients remains high. However, following resuscitation and correction of any acute hydrocephalus, a patient subgroup identified on simple clinical criteria can be identified who can expect a better outcome.

Adolescent↗
PubMed2000

Two estrogen receptors expressed in the teleost fish, Sparus aurata: cDNA cloning, characterization and tissue distribution.

Estrogen is an essential hormone for many reproductive and non-reproductive functions. The function of estrogen in the reproductive cycle of seabream (Sparus aurata), a protandrous hermaphrodite teleost fish, is complex but it is understood to be involved in sex inversion, a process that occurs in some individuals during the second reproductive season. Estrogen action is mediated by two estrogen receptor (ER) subtypes designated alpha and beta. As a step to understanding the mechanisms of estrogen action during natural and induced sex reversal in seabream, we have isolated two cDNAs encoding distinct forms of ER homologous to mammalian ERalpha and ERbeta. The seabream ERalpha clone (sbERalpha1), which was truncated in the A/B domain, corresponded to a variant differing in five amino acids from another recently cloned sbERalpha. The ERbeta clone (sbERbeta) encoded a protein 559 amino acids long and showed only 40% identity to sbERalpha. Northern blot analysis of liver and ovary mRNA indicated the presence of several transcripts of the two receptor subtypes. PCR analysis showed that the two receptors differed in their expression pattern. sbERalpha had a more restricted distribution, occurring mainly in testis, liver and heart, and sbERbeta was present in most tissues, being more abundant in ovary, testis, liver, intestine and kidney. The presence in seabream of two ERs with several ER transcripts and their pattern of distribution are consistent with the widespread effects of estrogen in different tissues.

Amino Acid Sequence↗
PubMed1999

Helical computed tomography and three-dimensional reconstruction of a bipedicular developmental anomaly of the C2 vertebra.

STUDY DESIGN: A case of bilateral failure of fusion of the C2 neural arch resembling a bipedicular fracture in a 9-year-old boy involved in a motor vehicle accident. OBJECTIVES: To describe the use of helical computed tomography and three-dimensional reconstruction images to identify the defect as congenital. SUMMARY OF BACKGROUND DATA: Congenital defects in the C2 neural arch are rare. Diagnostic difficulties arise when they are discovered during the assessment of patients after trauma, when they may resemble C2 arch fractures. METHODS: Lateral cervical spine radiograph, transverse section computed tomography, and three-dimensional reconstruction images were used to delineate the anatomy of the defect. RESULTS: The three-dimensional reconstruction views showed that normal alignment of the vertebrae was maintained, despite the pedicle defects. CONCLUSIONS: Differentiation of a C2 fracture from a congenital defect may be difficult. Reconstruction in three dimensions from helical computed tomography is a useful adjunct to conventional computed tomography in the evaluation of such patients.

Cervical Vertebrae↗
PubMed1999

Cloning, expression, and tissue localisation of prolactin in adult sea bream (Sparus aurata).

A major action of prolactin (PRL) in teleost fish is the maintenance of hydromineral balance in euryhaline species in fresh water. The function of PRL in marine teleosts is less certain and unlike euryhaline teleosts, such as tilapia and salmon, there is relatively little information about protein or gene structure. Associated with studies to determine potential functions of PRL, pituitary prolactin cDNA has been cloned and sequenced from sea bream (Sparus aurata), a marine teleost. The sequence obtained spanned 1349 bp and contained an open reading frame encoding a protein of 212 amino acids composed of a putative signal peptide of 24 residues and a mature protein of 188 amino acids. N-terminal sequencing of the native protein confirmed unambiguously the cleavage site, Ala24, Val25, predicted from alignments of the sea bream PRL cDNA with that of other teleosts. The presence of only one form of PRL in sea bream was supported by identification using Northern blots of only a single transcript of 1.35 kb. Reverse transcription and polymerase chain reaction techniques coupled with Southern blot analysis resulted in the detection of PRL in the pituitary but also in the intestine, liver, ovary, and testes.

Amino Acid Sequence↗
PubMed1999

Identification of transthyretin in fish (Sparus aurata): cDNA cloning and characterisation.

Transthyretin (TTR) has been proposed to have first evolved in reptiles and is one of the three plasma proteins important in the transport of thyroid hormones in higher vertebrates. A full-length cDNA encoding TTR was isolated from a sea bream (Sparus aurata) liver cDNA library using a homologous TTR cDNA probe generated by RT-PCR. Comparison of the deduced amino acid sequence of sea bream TTR with other published sequences, revealed an overall identity of 47-54%, although the amino acids in the active binding site were almost 100% conserved. Distribution of TTR was studied in sea bream adult tissue by RT-PCR and was detected in liver, brain, pituitary, gills, kidney, intestine and testis, although northern blot analysis only revealed TTR in the liver, suggesting that in sea bream, liver is the main source of this protein. TTR was also expressed in larvae from the first day post-hatch (48 h post-fertilisation). Analysis of thyroxine (T4) and triiodo-L-thyronine (T3) binding to sea bream serum proteins demonstrated that both T4 and T3 bind to albumin and TTR. By demonstrating the existence of TTR in teleost fish this study indicates TTR must have evolved in a common fish ancestor of the tetrapod evolutionary line.

Amino Acid Sequence↗